Vel factory function

def create(input_shape):
    """ Vel factory function """
    if isinstance(input_shape, numbers.Number):
        input_shape = (input_shape,)
    elif not isinstance(input_shape, tuple):
        input_shape = tuple(input_shape)

    def instantiate(**_):
        return NormalizeObservations(input_shape)

    return ModelFactory.generic(instantiate)