How to use the genie.metaparser.util.schemaengine.Optional function in genie

}
                            }
                        },
                        'pw': {
                            'num_pw': int,
                            'num_pw_up': int,
                        },
                        Optional('pbb'): {
                            'num_pbb': int,
                            'num_pbb_up': int,
                        },
                        Optional('vni'): {
                            'num_vni': int,
                            'num_vni_up': int,
                        },
                        Optional('evpn'): {
                            Any(): {
                                'state': str,
                            }
                        }
                    },
                }
            }
        }
    }

class ShowL2vpnBridgeDomain(ShowL2vpnBridgeDomainSchema):
    """Parser for show l2vpn bridge-domain"""

    cli_command = 'show l2vpn bridge-domain'
    def cli(self, output=None):
        if output is None:

Optional('load_balance'): {
                    Optional('load_balance'): str,
                    Optional('link_order_signaling'): str,
                    Optional('hash_type'): str,
                    Optional('locality_threshold'): str,
                },
                'lacp': {
                    'lacp': str,
                    Optional('flap_suppression_timer'): str,
                    Optional('cisco_extensions'): str,
                    Optional('non_revertive'): str,
                },
                'mlacp': {
                    'mlacp': str,
                    Optional('iccp_group'): str,
                    Optional('role'): str,
                    Optional('foreign_links_active'): int,
                    Optional('foreign_links_configured'): int,
                    Optional('switchover_type'): str,
                    Optional('recovery_delay'): str,
                    Optional('maximize_threshold'): str,
                },
                'ipv4_bfd': {
                    'ipv4_bfd': str,
                    Optional('state'): str,
                    Optional('fast_detect'): str,
                    Optional('start_timer'): str,
                    Optional('neighbor_unconfigured_timer'): str,
                    Optional('preferred_min_interval_ms'): int,
                    Optional('preferred_multiple'): int,
                    Optional('destination_address'): str,
                },

# ============================================
# Schema for '/dna/intent/api/v1/interface'
# ============================================
class InterfaceSchema(MetaParser):
    """schema for /dna/intent/api/v1/interface, /dna/intent/api/v1/interface/{interface}"""

    schema = {
        'hostname': {
            Any(): {
                'interfaces': {
                    Any(): {
                        "adminStatus": str,
                        Optional("className"): str,
                        Optional("description"): str,
                        "deviceId": str,
                        Optional("duplex"): str,
                        Optional("id"): str,
                        "ifIndex": str,
                        Optional("instanceTenantId"): str,
                        Optional("instanceUuid"): str,
                        "interfaceType": str,
                        Optional("ipv4Address"): str,
                        Optional("ipv4Mask"): str,
                        "isisSupport": str,
                        "lastUpdated": str,
                        Optional("macAddress"): str,
                        Optional("mappedPhysicalInterfaceId"): str,
                        Optional("mappedPhysicalInterfaceName"): str,
                        Optional("mediaType"): str,
                        Optional("nativeVlanId"): str,
                        "ospfSupport": str,
                        "pid": str,

},
                        Optional('l4'): {
                            Any(): {   # protocols
                                Optional('type'): int,
                                Optional('code'): int,
                                Optional('acknowledgement_number'): int,
                                Optional('data_offset'): int,
                                Optional('reserved'): int,
                                Optional('flags'): str,
                                Optional('window_size'): int,
                                Optional('urgent_pointer'): int,
                                Optional('options'): int,
                                Optional('options_name'): str,
                                Optional('established'): bool,
                                Optional('source_port'): {
                                    Optional('range'): {
                                        'lower_port': int,
                                        'upper_port': int,
                                    },
                                    Optional('operator'): {
                                        'operator': str,
                                        'port': str,
                                    }
                                },
                                Optional('destination_port'): {
                                   Optional('range'): {
                                        'lower_port': int,
                                        'upper_port': int,
                                    },
                                    Optional('operator'): {
                                        'operator': str,                                        
                                        'port': int,

# Pass firmware list as value
        if not isinstance(value, list):
            raise SchemaTypeError('inner chassis hardware is not a list')
        chassis_inner_hardware_schema = Schema(
                        {
                            Optional("chassis-sub-sub-module"): {
                                "description": str,
                                "name": str,
                                "part-number": str,
                                "serial-number": str
                            },
                            Optional("description"): str,
                            "name": str,
                            Optional("part-number"): str,
                            Optional("serial-number"): str,
                            Optional("version"): str
                        }
                    
        )
        # Validate each dictionary in list
        for item in value:
            chassis_inner_hardware_schema.validate(item)
        return value

Optional("active-defects"): {
                Optional("interface-alarms"): {
                    Optional("alarm-not-present"): bool,
                    Optional("ethernet-alarm-link-down"): bool
                }
            },
            Optional("admin-status"): {
                Optional("#text"): str,
                Optional("@junos:format"): str
            },
            Optional("bpdu-error"): str,
            Optional("clocking"): str,
            Optional("current-physical-address"): str,
            Optional("description"): str,
            Optional("eth-switch-error"): str,
            Optional("ethernet-fec-mode"): {
                Optional("@junos:style"): str,
                "enabled_fec_mode": str
            },
            Optional("ethernet-fec-statistics"): {
                Optional("@junos:style"): str,
                "fec_ccw_count": str,
                "fec_ccw_error_rate": str,
                "fec_nccw_count": str,
                "fec_nccw_error_rate": str
            },
            Optional("ethernet-pcs-statistics"): {
                Optional("@junos:style"): str,
                "bit-error-seconds": str,
                "errored-blocks-seconds": str
            },
            Optional("hardware-physical-address"): str,

"output-mac-control-frames": str,
                    "output-mac-pause-frames": str,
                    "output-multicasts": str,
                    "output-packets": str,
                    Optional("output-total-errors"): str,
                    "output-unicasts": str
            },
            Optional("input-error-list"): {
                    Optional("framing-errors"): str,
                    Optional("input-discards"): str,
                    Optional("input-drops"): str,
                    Optional("input-errors"): str,
                    Optional("input-fifo-errors"): str,
                    Optional("input-giants"): str,
                    Optional("input-l2-channel-errors"): str,
                    Optional("input-l2-mismatch-timeouts"): str,
                    Optional("input-l3-incompletes"): str,
                    Optional("input-resource-errors"): str,
                    Optional("input-runts"): str
            },
            Optional("transit-traffic-statistics"): {
                "input-bps": str,
                "input-bytes": str,
                "input-packets": str,
                "input-pps": str,
                Optional("ipv6-transit-statistics"): {
                    "input-bps": str,
                    "input-bytes": str,
                    "input-packets": str,
                    "input-pps": str,
                    "output-bps": str,
                    "output-bytes": str,

{
                    'accepted-prefix-count': str,
                    'active-prefix-count': str,
                    'name': str,
                    'received-prefix-count': str,
                    'suppressed-prefix-count': str
                }
            )

            for item in value:
                bgp_peer_rib_schema.validate(item)
            return value

        bgp_peer_schema = Schema(
            {
                Optional('bgp-rib'): Use(validate_bgp_peer_rib_list),
                Optional("description"): str,
                "elapsed-time": {
                    "#text": str,
                    Optional("@junos:seconds"): str,
                },
                "flap-count": str,
                "input-messages": str,
                "output-messages": str,
                "peer-address": str,
                "peer-as": str,
                "peer-state": str,
                "route-queue-count": str,
            }
        )
        for item in value:
            bgp_peer_schema.validate(item)

'multicast_group': str,
                                'distance': int,
                                Optional('timers'): {
                                    Optional('update_interval'): int,
                                    Optional('expire_in'): int,
                                    Optional('collect_garbage'): int,
                                },
                                'default_metric': int,
                                'maximum_paths': int,
                                Optional('default_originate'): str,
                                'process': str,
                                Optional('interfaces'): {
                                    Any(): {
                                    },
                                },
                                Optional('redistribute'): {
                                    Any(): {
                                        Optional('route_policy'): str,
                                    },
                                },
                            },
                        },
                    },
                },
            },
        },
    }


class ShowIpRipVrfAll(ShowIpRipVrfAllSchema):
    """Parser for:
        * show ip rip

schema = {
                Optional('main'): {
                    Optional('switch_mac_address'): str,
                    Optional('mac_persistency_wait_time'): str,
                    Optional('chassis'): str
                },
                'slot': {
                    Any(): {
                        Optional('rp'): {
                            Any(): {
                                Optional('sn'): str,
                                'state': str,
                                Optional('num_of_ports'): str,
                                Optional('mac_address'): str,
                                Optional('hw_ver'): str,
                                Optional('sw_ver'): str,
                                Optional('swstack_role'): str,
                                Optional('swstack_priority'): str,
                                Optional('ports'): str,
                                Optional('role'): str,
                                Optional('name'): str,
                                Optional('slot'): str,
                                Optional('priority'): str,
                                Optional('insert_time'): str,
                                Optional('fw_ver'): str,
                                Optional('cpld_ver'): str,
                            }
                        },
                        Optional('lc'): {
                            Any(): {
                                Optional('cpld_ver'): str,
                                Optional('fw_ver'): str,