code: def regular_expressions_entities(self):
          
          domain = 0
          if domain not in self.domains:
              self.register_domain(domain=domain)
          return self.domains[domain].regular_expressions_entities
docs: A property to link into IntentEngine's regular_expressions_entities.
  
          Warning: this is only for backwards compatiblility and should not be used if you
              intend on using domains.
  
          Returns: the domains regular_expression_entities from its IntentEngine