code: def lowercase(state):
      
      return state.to_child(
          student_result={k.lower(): v for k, v in state.student_result.items()},
          solution_result={k.lower(): v for k, v in state.solution_result.items()},
      )
docs: Convert all column names to their lower case versions to improve robustness
      
      :Example:
  
          Suppose we are testing the following SELECT statements
  
          * solution: ``SELECT artist_id as id FROM artists``
          * student : ``SELECT artist_id as ID FROM artists``
  
          We can write the following SCTs: ::
  
              # fails, as id and ID have different case
              Ex().check_column('id').has_equal_value()
  
              # passes, as lowercase() is being used
              Ex().lowercase().check_column('id').has_equal_value()