Must include a ``manifestationOfWork`` key.

def is_manifestation_model(instance, attribute, value):
    """Must include a ``manifestationOfWork`` key."""

    instance_name = instance.__class__.__name__
    is_creation_model(instance, attribute, value)

    manifestation_of = value.get('manifestationOfWork')
    if not isinstance(manifestation_of, str):
        err_str = ("'manifestationOfWork' must be given as a string in the "
                   "'{attr}' parameter of a '{cls}'. Given "
                   "'{value}'").format(attr=attribute.name,
                                       cls=instance_name,
                                       value=manifestation_of)
        print(err_str)