code: def table(self):
          
          if hasattr(self.data, 'table_on') and self.data.table_on:
              assert_index_sane(self.data.table, len(self.song.tables))
              return self.song.tables[self.data.table]
docs: a ```pylsdj.Table``` referencing the instrument's table, or None
          if the instrument doesn't have a table