code: def _call(self, x, out=None):
          
          if out is None:
              return self.operator(self.scalar * x)
          else:
              if self.__tmp is not None:
                  tmp = self.__tmp
              else:
                  tmp = self.domain.element()
              tmp.lincomb(self.scalar, x)
              self.operator(tmp, out=out)
docs: Implement ``self(x[, out])``.