def is_valid(self):
if self._django_user is not None:<EOL><INDENT>return self._django_user.is_authenticated()<EOL><DEDENT>else:<EOL><INDENT>return False<EOL><DEDENT>
Tests whether or not the credential represented by this ``Authentication`` is currently valid.

        A credential may be invalid because it has been destroyed,
        expired, or is somehow no longer able to be used.

        return: (boolean) - ``true`` if this authentication credential
                is valid, ``false`` otherwise
        *compliance: mandatory -- This method must be implemented.*
        *implementation notes*: Any problem in determining the validity
        of this credential should result in ``false``.