code: def _get_dataframe(self):
          
          if self.source_conn is None:  # Use local file
              return ge.read_csv(self.dataset_name, **self.dataset_params)
  
          if isinstance(self.source_conn, S3Hook):
              hook = ExpectationS3CsvHook(aws_conn_id=self.source_conn_id)
  
              return hook.get_ge_df(self.dataset_name, self.source_bucket_name, **self.dataset_params)
  
          if isinstance(self.source_conn, DbApiHook):
              hook = ExpectationMySQLHook(mysql_conn_id=self.source_conn_id)
  
              return hook.get_ge_df(self.dataset_name, **self.dataset_params)
docs: Load dataframe based on specified connection
          :return: