code: def re(self, event_property, value):
          
          c = self.copy()
          c.filters.append(filters.RE(event_property, value))
          return c
docs: A regular expression filter chain.
  
          >>> request_time = EventExpression('request', 'elapsed_ms')
          >>> filtered = request_time.re('path', '[^A-Za-z0-9+]')
          >>> print(filtered)
          request(elapsed_ms).re(path, "[^A-Za-z0-9+]")