def is_derived_from(self, fromclause):
        """Return True if this FromClause is 'derived' from the given
        FromClause.

        An example would be an Alias of a Table is derived from that Table.

        """
        # this is essentially an "identity" check in the base class.
        # Other constructs override this to traverse through
        # contained elements.
        return fromclause in self._cloned_set
dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/sql/selectable.py/FromClause.is_derived_from/original