Return a fully-qualified role_assignment string.

def role_assignment_path(cls, project, incident, role_assignment):
        """Return a fully-qualified role_assignment string."""
        return google.api_core.path_template.expand(
            "projects/{project}/incidents/{incident}/roleAssignments/{role_assignment}",
            project=project,
            incident=incident,
            role_assignment=role_assignment,
        )