code: def first(self):
          
          pairs = self.resolve()
          try:
              return iter_first(pairs)
          except ValueError:
              raise NotFoundError(u"{0} not found".format(self.name))
docs: Return a (value, source) pair for the first object found for
          this view. This amounts to the first element returned by
          `resolve`. If no values are available, a NotFoundError is
          raised.