@staticmethod
def get_output_codes():
    """Return a list of all possible output codes."""
    return ['interface-added', 'interface-removed', 'deprecated',
        'undeprecatedc-symbol-changed', 'reply-added', 'reply-removed',
        'ecs-changed-true-invalidates', 'ecs-changed-true-false',
        'ecs-changed-true-const', 'ecs-changed-invalidates-true',
        'ecs-changed-invalidates-false', 'ecs-changed-invalidates-const',
        'ecs-changed-false-invalidates', 'ecs-changed-false-true',
        'ecs-changed-false-const', 'ecs-changed-const-invalidates',
        'ecs-changed-const-true', 'ecs-changed-const-false', 'method-added',
        'method-removed', 'property-added', 'property-removed',
        'signal-added', 'signal-removed', 'argument-added',
        'argument-removed', 'property-type-changed',
        'property-access-changed-read-readwrite',
        'property-access-changed-read-write',
        'property-access-changed-write-read',
        'property-access-changed-write-readwrite',
        'property-access-changed-readwrite-read',
        'property-access-changed-readwrite-write', 'argument-name-changed',
        'argument-type-changed', 'argument-direction-changed-in-out',
        'argument-direction-changed-out-in']
