docs: def blocking(self):
          """
          Display queries holding locks other queries are waiting to be
          released.
  
          Record(
              pid=40821,
              source='',
              running_for=datetime.timedelta(0, 0, 2857),
              waiting=False,
              query='SELECT pg_sleep(10);'
          )
  
          :returns: list of Records
          """
  
          return self.execute(
              sql.BLOCKING.format(
                  query_column=self.query_column,
                  pid_column=self.pid_column
              )
          )