docs: def check(self):
      """
        Type check this object.
      """
      try:
        si, uninterp = self.interpolate()
      # TODO(wickman) This should probably be pushed out to the interpolate leaves.
      except (Object.CoercionError, MustacheParser.Uninterpolatable) as e:
        return TypeCheck(False, "Unable to interpolate: %s" % e)
      return self.checker(si)