code: def source(self, request):
          
          if isinstance(self.location, six.string_types):
              value = getattr(request, self.location, MultiDict())
              if callable(value):
                  value = value()
              if value is not None:
                  return value
          else:
              values = MultiDict()
              for l in self.location:
                  value = getattr(request, l, None)
                  if callable(value):
                      value = value()
                  if value is not None:
                      values.update(value)
              return values
  
          return MultiDict()
docs: Pulls values off the request in the provided location
          :param request: The flask request object to parse arguments from