def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def __exit__(self, exc_type, exc_val, exc_tb):
        connection = connections[get_tenant_database_alias()]

        connection.set_tenant(self._previous_tenant.pop())