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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 hook_alias(self, alias, model_obj=None):
        '''
        Returns the alias function, if it exists and if it can be applied to this model.
        '''
        try:
            search_alias = self._alias_hooks[alias]
        except KeyError:
            raise AttributeError('Could not find search alias named {}. Is this alias defined in BUNGIESEARCH["ALIASES"]?'.format(alias))
        else:
            if search_alias._applicable_models and \
                ((model_obj and model_obj not in search_alias._applicable_models) or \
                 not any([app_model_obj.__name__ in self._doc_type for app_model_obj in search_alias._applicable_models])):
                    raise ValueError('Search alias {} is not applicable to model/doc_types {}.'.format(alias, model_obj if model_obj else self._doc_type))
            return search_alias.prepare(self, model_obj).alias_for