code: def test_collect_to_container_collections_with_multiple_elements_preserves_only_one_element(
      self,
  ):
      # We don't use beam package methods and TestPipeline because in
      # beam_util there is no assertIn method.
      col_x = [2, 1]
      col_y = ["str1", "str2"]
      col_z = [["str1", "str2"], ["str3", "str4"]]
  
      container = composite_funcs.collect_to_container(
          self.backend,
          {"x": col_x, "y": col_y, "z": col_z},
          TestContainer,
          "Collect to container",
      )
  
      container: TestContainer = list(container)[0]
      self.assertIn(container.x, col_x)
      self.assertIn(container.y, col_y)
      self.assertIn(container.z, col_z)
  
imports: import sys
  import unittest
  from dataclasses import dataclass
  from typing import List
  import apache_beam
  import apache_beam.testing.test_pipeline
  import apache_beam.testing.util
  from absl.testing import parameterized
  import pipeline_dp
  from pipeline_dp import pipeline_functions
  from pipeline_dp import pipeline_backend
label_desc: Use image node_id 5 for calling the BeamBackendTest obj's underlying member method code with example usage: obj.test_collect_to_container_collections_with_multiple_elements_preserves_only_one_element() without return types