code: def _begin_request(self):
          
          headers = self.m2req.headers
  
          self._request = HTTPRequest(connection=self,
              method=headers.get("METHOD"),
              uri=self.m2req.path,
              version=headers.get("VERSION"),
              headers=headers,
              remote_ip=headers.get("x-forwarded-for"))
  
          if len(self.m2req.body) > 0:
              self._request.body = self.m2req.body
  
          if self.m2req.is_disconnect():
              self.finish()
  
          elif headers.get("x-mongrel2-upload-done", None):
              # there has been a file upload.
              expected = headers.get("x-mongrel2-upload-start", "BAD")
              upload = headers.get("x-mongrel2-upload-done", None)
  
              if expected == upload:
                  self.request_callback(self._request)
  
          elif headers.get("x-mongrel2-upload-start", None):
              # this is just a notification that a file upload has started. Do
              # nothing for now!
              pass
  
          else:
              self.request_callback(self._request)
docs: Actually start executing this request.