@abc.abstractmethod<EOL><INDENT>def has_parents(self):<DEDENT>
return<EOL>
Tests if any parents are available in this node structure.

        There may be no more parents in this node structure however
        there may be parents that exist in the hierarchy.

        :return: ``true`` if this node has parents, ``false`` otherwise
        :rtype: ``boolean``


        *compliance: mandatory -- This method must be implemented.*