code: def make_null_event_date_events(all_sids, timestamp):
      """
      Make an event with a null event_date for all sids.
  
      Used to test that EventsLoaders filter out null events.
      """
      return pd.DataFrame(
          {
              "sid": all_sids,
              "timestamp": timestamp,
              "event_date": pd.Timestamp("NaT"),
              "float": -9999.0,
              "int": -9999,
              "datetime": pd.Timestamp("1980"),
              "string": "should be ignored",
          }
      )
  
imports: from datetime import time
  from itertools import product
  from unittest import skipIf
  import blaze
  import numpy
  import pandas
  import pytz
  from zipline.pipeline import Pipeline, SimplePipelineEngine
  from zipline.pipeline.common import EVENT_DATE_FIELD_NAME, TS_FIELD_NAME, SID_FIELD_NAME
  from zipline.pipeline.data import DataSet, Column
  from zipline.pipeline.domain import US_EQUITIES, EquitySessionDomain
  from zipline.pipeline.loaders.events import EventsLoader
  from zipline.pipeline.loaders.blaze.events import BlazeEventsLoader
  from zipline.pipeline.loaders.utils import next_event_indexer, previous_event_indexer
  from zipline.testing import ZiplineTestCase
  from zipline.testing.fixtures import WithAssetFinder, WithTradingSessions
  from zipline.testing.predicates import assert_equal
  from zipline.utils.numpy_utils import categorical_dtype, datetime64ns_dtype, float64_dtype, int64_dtype
  from zipline.utils.pandas_utils import new_pandas, skip_pipeline_new_pandas
label_desc: Use image node_id 2 for calling a global function with example usage: make_null_event_date_events(all_sids, timestamp) and returns: pd