code: def get_body_argument(
          self,
          name: str,
          default: Union[None, str, _ArgDefaultMarker] = _ARG_DEFAULT,
          strip: bool = True,
      ) -> Optional[str]:
          
          return self._get_argument(name, default, self.request.body_arguments, strip)
docs: Returns the value of the argument with the given name
          from the request body.
  
          If default is not provided, the argument is considered to be
          required, and we raise a `MissingArgumentError` if it is missing.
  
          If the argument appears in the url more than once, we return the
          last value.
  
          .. versionadded:: 3.2