code: def value(self, view, template=None):
          
          if view.exists():
              value, _ = view.first()
              return self.convert(value, view)
          elif self.default is REQUIRED:
              # Missing required value. This is an error.
              raise NotFoundError(u"{0} not found".format(view.name))
          else:
              # Missing value, but not required.
              return self.default
docs: Get the value for a `ConfigView`.
  
          May raise a `NotFoundError` if the value is missing (and the
          template requires it) or a `ConfigValueError` for invalid values.