How to use the nitpick.fields.Dict function in nitpick

class SetupCfgSchema(BaseNitpickSchema):
    """Validation schema for setup.cfg."""

    error_messages = {"unknown": help_message("Unknown configuration", "nitpick_section.html#comma-separated-values")}

    comma_separated_values = fields.List(fields.String(validate=fields.validate_section_dot_field))


class NitpickFilesSectionSchema(BaseNitpickSchema):
    """Validation schema for the ``[nitpick.files]`` section on the style file."""

    error_messages = {"unknown": help_message("Unknown file", "nitpick_section.html#nitpick-files")}

    absent = fields.Dict(fields.NonEmptyString, fields.String())
    present = fields.Dict(fields.NonEmptyString, fields.String())
    # TODO: load this schema dynamically, then add this next field setup_cfg
    setup_cfg = fields.Nested(SetupCfgSchema, data_key=SetupCfgPlugin.file_name)


class NitpickSectionSchema(BaseNitpickSchema):
    """Validation schema for the ``[nitpick]`` section on the style file."""

    minimum_version = fields.NonEmptyString()
    styles = fields.Nested(NitpickStylesSectionSchema)
    files = fields.Nested(NitpickFilesSectionSchema)


class BaseStyleSchema(Schema):
    """Base validation schema for style files. Dynamic fields will be added to it later."""

def file_field_pair(file_name: str, base_file_class: Type[NitpickPlugin]) -> Dict[str, fields.Field]:
        """Return a schema field with info from a config file class."""
        valid_toml_key = TOMLFormat.group_name_for(file_name)
        unique_file_name_with_underscore = slugify(file_name, separator="_")

        kwargs = {"data_key": valid_toml_key}
        if base_file_class.validation_schema:
            field = fields.Nested(base_file_class.validation_schema, **kwargs)
        else:
            # For default files (pyproject.toml, setup.cfg...), there is no strict schema;
            # it can be anything they allow.
            # It's out of Nitpick's scope to validate those files.
            field = fields.Dict(fields.String, **kwargs)
        return {unique_file_name_with_underscore: field}

class SetupCfgSchema(BaseNitpickSchema):
    """Validation schema for setup.cfg."""

    error_messages = {"unknown": help_message("Unknown configuration", "nitpick_section.html#comma-separated-values")}

    comma_separated_values = fields.List(fields.String(validate=fields.validate_section_dot_field))


class NitpickFilesSectionSchema(BaseNitpickSchema):
    """Validation schema for the ``[nitpick.files]`` section on the style file."""

    error_messages = {"unknown": help_message("Unknown file", "nitpick_section.html#nitpick-files")}

    absent = fields.Dict(fields.NonEmptyString, fields.String())
    present = fields.Dict(fields.NonEmptyString, fields.String())
    # TODO: load this schema dynamically, then add this next field setup_cfg
    setup_cfg = fields.Nested(SetupCfgSchema, data_key=SetupCfgPlugin.file_name)


class NitpickSectionSchema(BaseNitpickSchema):
    """Validation schema for the ``[nitpick]`` section on the style file."""

    minimum_version = fields.NonEmptyString()
    styles = fields.Nested(NitpickStylesSectionSchema)
    files = fields.Nested(NitpickFilesSectionSchema)


class BaseStyleSchema(Schema):
    """Base validation schema for style files. Dynamic fields will be added to it later."""

    error_messages = {"unknown": help_message("Unknown file", "config_files.html")}

from nitpick.generic import flatten, unflatten
from nitpick.plugins import hookimpl
from nitpick.plugins.base import NitpickPlugin
from nitpick.schemas import BaseNitpickSchema
from nitpick.typedefs import JsonDict, YieldFlake8Error

KEY_CONTAINS_KEYS = "contains_keys"
KEY_CONTAINS_JSON = "contains_json"
LOGGER = logging.getLogger(__name__)


class JSONFileSchema(BaseNitpickSchema):
    """Validation schema for any JSON file added to the style."""

    contains_keys = fields.List(fields.NonEmptyString)
    contains_json = fields.Dict(fields.NonEmptyString, fields.JSONString)


class JSONPlugin(NitpickPlugin):
    """Checker for any JSON file.

    Add the configurations for the file name you wish to check.
    Example: :ref:`the default config for package.json `.
    """

    error_base_number = 340

    validation_schema = JSONFileSchema
    identify_tags = {"json"}

    SOME_VALUE_PLACEHOLDER = ""