How to use the grafanalib.core.Pixels function in grafanalib

# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import re
import attr
from grafanalib import core as g

DECREASING_ORDER_TOOLTIP = g.Tooltip(sort=g.SORT_DESC)
PANEL_HEIGHT = g.Pixels(300)
QUANTILES = [0.99, 0.9, 0.5]

SOURCE_TEMPLATE = g.Template(name="source", type="datasource", query="prometheus")


@attr.s
class Dashboard(g.Dashboard):
    time = attr.ib(default=g.Time("now-30d", "now"))
    # Make it possible to use $source as a source.
    templating = attr.ib(default=g.Templating(list=[SOURCE_TEMPLATE]))


# Graph is a g.Graph with reasonable defaults applied.
@attr.s
class Graph(g.Graph):
    dataSource = attr.ib(default="$source")

:param triggerSeverity: defines colors for trigger severity,
    :param triggers: trigger query

    """
    dataSource = attr.ib()
    title = attr.ib()

    ackEventColor = attr.ib(default=attr.Factory(lambda: BLANK),
                            validator=instance_of(RGBA))
    ageField = attr.ib(default=True, validator=instance_of(bool))
    customLastChangeFormat = attr.ib(default=False,
                                     validator=instance_of(bool))
    description = attr.ib(default="", validator=instance_of(str))
    fontSize = attr.ib(default=attr.Factory(Percent),
                       validator=instance_of(Percent))
    height = attr.ib(default=DEFAULT_ROW_HEIGHT, validator=instance_of(Pixels))
    hideHostsInMaintenance = attr.ib(default=False,
                                     validator=instance_of(bool))
    hostField = attr.ib(default=True, validator=instance_of(bool))
    hostTechNameField = attr.ib(default=False, validator=instance_of(bool))
    id = attr.ib(default=None)
    infoField = attr.ib(default=True, validator=instance_of(bool))
    lastChangeField = attr.ib(default=True, validator=instance_of(bool))

    lastChangeFormat = attr.ib(default="")
    limit = attr.ib(default=10, validator=instance_of(int))
    links = attr.ib(default=attr.Factory(list),
                    validator=is_list_of(DashboardLink))
    markAckEvents = attr.ib(default=False, validator=instance_of(bool))
    minSpan = attr.ib(default=None)
    okEventColor = attr.ib(default=attr.Factory(lambda: GREEN),
                           validator=instance_of(RGBA))

NULL_AS_ZERO = 'null as zero'
NULL_AS_NULL = 'null'

FLOT = 'flot'

ABSOLUTE_TYPE = 'absolute'
DASHBOARD_TYPE = 'dashboard'
GRAPH_TYPE = 'graph'
SINGLESTAT_TYPE = 'singlestat'
TABLE_TYPE = 'table'
TEXT_TYPE = 'text'
ALERTLIST_TYPE = "alertlist"

DEFAULT_FILL = 1
DEFAULT_REFRESH = '10s'
DEFAULT_ROW_HEIGHT = Pixels(250)
DEFAULT_LINE_WIDTH = 2
DEFAULT_POINT_RADIUS = 5
DEFAULT_RENDERER = FLOT
DEFAULT_STEP = 10
DEFAULT_LIMIT = 10
TOTAL_SPAN = 12

DARK_STYLE = 'dark'
LIGHT_STYLE = 'light'

UTC = 'utc'

SCHEMA_VERSION = 12

# Y Axis formats
DURATION_FORMAT = "dtdurations"

@attr.s
class Row(object):
    # TODO: jml would like to separate the balancing behaviour from this
    # layer.
    panels = attr.ib(default=attr.Factory(list), converter=_balance_panels)
    collapse = attr.ib(
        default=False, validator=instance_of(bool),
    )
    editable = attr.ib(
        default=True, validator=instance_of(bool),
    )
    height = attr.ib(
        default=attr.Factory(lambda: DEFAULT_ROW_HEIGHT),
        validator=instance_of(Pixels),
    )
    showTitle = attr.ib(default=None)
    title = attr.ib(default=None)
    repeat = attr.ib(default=None)

    def _iter_panels(self):
        return iter(self.panels)

    def _map_panels(self, f):
        return attr.evolve(self, panels=list(map(f, self.panels)))

    def to_json_data(self):
        showTitle = False
        title = "New row"
        if self.title is not None:
            showTitle = True