new_contents: import pandas as pd
  from pandas.io import gbq
  
  def test_tables_have_data(dataset, project_id, concepts):
      """Verifies each table has data."""
  
      for folder, concept_list in concepts.items():
          for concept_name in concept_list:
              query = f"""
              SELECT *
              FROM {dataset}.{concept_name}
              LIMIT 5
              """
              df = gbq.read_gbq(query, project_id=project_id, dialect="standard")
              assert df.shape[0] > 0, f'did not find table for {folder}.{concept_name}'
  
subject: add test asserting all derived tables have rows