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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 get_first_category(app_uid):
        '''
        Get the first, as the uniqe category of post.
        '''
        recs = MPost2Catalog.query_by_entity_uid(app_uid).objects()
        if recs.count() > 0:
            return recs.get()

        return None