docs: def columns(self):
          """
          :return: the list of column in this table
          """
          c = self._connection.cursor()
          c.execute("describe `%s`.`%s`" % (self._db, self._name))
          self._cols = []
          for col in c.fetchall():
              self._cols.append(Column.build(col, table=self, con=self._connection))
          return self._cols