code: def _call(self, x):
          
          if self.operator is None:
              return self.vector.inner(x) + self.constant
          elif self.vector is None:
              return x.inner(self.operator(x)) + self.constant
          else:
              tmp = self.operator(x)
              tmp += self.vector
              return x.inner(tmp) + self.constant
docs: Return ``self(x)``.