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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register_entity(self, entity_value, entity_type, alias_of=None, domain=0):
 """ Register an entity to be tagged in potential parse results. Args: entity_value(str):
 the value/proper name of an entity instance (Ex: "The Big Bang Theory") entity_type(str):
 the type/tag of an entity instance (Ex: "Television Show") domain(str):
 a string representing the domain you wish to add the entity to """

        if domain not in self.domains:
            self.register_domain(domain=domain)
        self.domains[domain].register_entity(entity_value=entity_value,
                                             entity_type=entity_type,
                                             alias_of=alias_of)