How to use the pydruid.utils.postaggregator.Postaggregator function in pydruid

self.assertEqual(postagg.name, "postagg_name")
        self.assertEqual(postagg.post_aggregator["value"], 1234)
        # hyperUniqueCardinality
        conf = {"type": "hyperUniqueCardinality", "name": "unique_name"}
        postagg = get_post_agg(conf)
        self.assertTrue(isinstance(postagg, postaggs.HyperUniqueCardinality))
        self.assertEqual(postagg.name, "unique_name")
        # arithmetic
        conf = {
            "type": "arithmetic",
            "fn": "+",
            "fields": ["field1", "field2"],
            "name": "postagg_name",
        }
        postagg = get_post_agg(conf)
        self.assertTrue(isinstance(postagg, postaggs.Postaggregator))
        self.assertEqual(postagg.name, "postagg_name")
        self.assertEqual(postagg.post_aggregator["fn"], "+")
        self.assertEqual(postagg.post_aggregator["fields"], ["field1", "field2"])
        # custom post aggregator
        conf = {"type": "custom", "name": "custom_name", "stuff": "more_stuff"}
        postagg = get_post_agg(conf)
        self.assertTrue(isinstance(postagg, models.CustomPostAggregator))
        self.assertEqual(postagg.name, "custom_name")
        self.assertEqual(postagg.post_aggregator["stuff"], "more_stuff")

for metric_name in metrics:
            metric = metrics_dict[metric_name]
            if metric.metric_type != 'postagg':
                all_metrics.append(metric_name)
            else:
                conf = metric.json_obj
                all_metrics += recursive_get_fields(conf)
                all_metrics += conf.get('fieldNames', [])
                if conf.get('type') == 'javascript':
                    post_aggs[metric_name] = JavascriptPostAggregator(
                        name=conf.get('name'),
                        field_names=conf.get('fieldNames'),
                        function=conf.get('function'))
                else:
                    post_aggs[metric_name] = Postaggregator(
                        conf.get('fn', "/"),
                        conf.get('fields', []),
                        conf.get('name', ''))

        aggregations = OrderedDict()
        for m in self.metrics:
            if m.metric_name in all_metrics:
                aggregations[m.metric_name] = m.json_obj

        rejected_metrics = [
            m.metric_name for m in self.metrics
            if m.is_restricted and
            m.metric_name in aggregations.keys() and
            not sm.has_access('metric_access', m.perm)
        ]

import requests
except ImportError:
    pass

try:
    from superset.utils.core import DimSelector, DTTM_ALIAS, flasher
except ImportError:
    pass

DRUID_TZ = conf.get("DRUID_TZ")
POST_AGG_TYPE = "postagg"
metadata = Model.metadata  # pylint: disable=no-member

try:
    # Postaggregator might not have been imported.
    class JavascriptPostAggregator(Postaggregator):
        def __init__(self, name, field_names, function):
            self.post_aggregator = {
                "type": "javascript",
                "fieldNames": field_names,
                "name": name,
                "function": function,
            }
            self.name = name

    class CustomPostAggregator(Postaggregator):
        """A way to allow users to specify completely custom PostAggregators"""

        def __init__(self, name, post_aggregator):
            self.name = name
            self.post_aggregator = post_aggregator

conf.get('name', ''),
                        conf.get('probabilities', ''),
                    )
                elif conf.get('type') == 'fieldAccess':
                    post_aggs[metric_name] = Field(conf.get('name'), '')
                elif conf.get('type') == 'constant':
                    post_aggs[metric_name] = Const(
                        conf.get('value'),
                        output_name=conf.get('name', '')
                    )
                elif conf.get('type') == 'hyperUniqueCardinality':
                    post_aggs[metric_name] = HyperUniqueCardinality(
                        conf.get('name'), ''
                    )
                else:
                    post_aggs[metric_name] = Postaggregator(
                        conf.get('fn', "/"),
                        conf.get('fields', []),
                        conf.get('name', ''))

        aggregations = OrderedDict()
        for m in self.metrics:
            if m.metric_name in all_metrics:
                aggregations[m.metric_name] = m.json_obj

        rejected_metrics = [
            m.metric_name for m in self.metrics
            if m.is_restricted and
            m.metric_name in aggregations.keys() and
            not sm.has_access('metric_access', m.perm)
        ]

name=mconf.get("name", ""),
                field_names=mconf.get("fieldNames", []),
                function=mconf.get("function", ""),
            )
        elif mconf.get("type") == "quantile":
            return Quantile(mconf.get("name", ""), mconf.get("probability", ""))
        elif mconf.get("type") == "quantiles":
            return Quantiles(mconf.get("name", ""), mconf.get("probabilities", ""))
        elif mconf.get("type") == "fieldAccess":
            return Field(mconf.get("name"))
        elif mconf.get("type") == "constant":
            return Const(mconf.get("value"), output_name=mconf.get("name", ""))
        elif mconf.get("type") == "hyperUniqueCardinality":
            return HyperUniqueCardinality(mconf.get("name"))
        elif mconf.get("type") == "arithmetic":
            return Postaggregator(
                mconf.get("fn", "/"), mconf.get("fields", []), mconf.get("name", "")
            )
        else:
            return CustomPostAggregator(mconf.get("name", ""), mconf)

for metric_name in metrics:
            metric = metrics_dict[metric_name]
            if metric.metric_type != 'postagg':
                all_metrics.append(metric_name)
            else:
                conf = metric.json_obj
                all_metrics += recursive_get_fields(conf)
                all_metrics += conf.get('fieldNames', [])
                if conf.get('type') == 'javascript':
                    post_aggs[metric_name] = JavascriptPostAggregator(
                        name=conf.get('name'),
                        field_names=conf.get('fieldNames'),
                        function=conf.get('function'))
                else:
                    post_aggs[metric_name] = Postaggregator(
                        conf.get('fn', "/"),
                        conf.get('fields', []),
                        conf.get('name', ''))

        aggregations = {
            m.metric_name: m.json_obj
            for m in self.metrics
            if m.metric_name in all_metrics
        }

        rejected_metrics = [
            m.metric_name for m in self.metrics
            if m.is_restricted and
            m.metric_name in aggregations.keys() and
            not sm.has_access('metric_access', m.perm)
        ]

link_table = target.__table__
        connection.execute(
            link_table.update()
            .where(link_table.c.id == target.id)
            .values(perm=target.get_perm())
        )


def set_related_perm(mapper, connection, target):  # noqa
    src_class = target.cls_model
    id_ = target.datasource_id
    ds = db.session.query(src_class).filter_by(id=int(id_)).first()
    target.perm = ds.perm


class JavascriptPostAggregator(Postaggregator):
    def __init__(self, name, field_names, function):
        self.post_aggregator = {
            'type': 'javascript',
            'fieldNames': field_names,
            'name': name,
            'function': function,
        }
        self.name = name


class ImportMixin(object):
    def override(self, obj):
        """Overrides the plain fields of the dashboard."""
        for field in obj.__class__.export_fields:
            setattr(self, field, getattr(obj, field))

FillterPattern = re.compile(r'''((?:[^,"']|"[^"]*"|'[^']*')+)''')


def set_perm(mapper, connection, target):  # noqa
    if target.perm != target.get_perm():
        link_table = target.__table__
        connection.execute(
            link_table.update()
            .where(link_table.c.id == target.id)
            .values(perm=target.get_perm())
        )


class JavascriptPostAggregator(Postaggregator):
    def __init__(self, name, field_names, function):
        self.post_aggregator = {
            'type': 'javascript',
            'fieldNames': field_names,
            'name': name,
            'function': function,
        }
        self.name = name


class ImportMixin(object):
    def override(self, obj):
        """Overrides the plain fields of the dashboard."""
        for field in obj.__class__.export_fields:
            setattr(self, field, getattr(obj, field))