'Get scope information.
Verify and return the scoping information.
:returns: (domain_id, project_id, trust_ref, unscoped).
If scope to a project, (None, project_id, None, None)
will be returned.
If scoped to a domain, (domain_id, None, None, None)
will be returned.
If scoped to a trust, (None, project_id, trust_ref, None),
Will be returned, where the project_id comes from the
trust definition.
If unscoped, (None, None, None, \'unscoped\') will be
returned.'

def get_scope(self):

    return self._scope_data
