class_docstr: Squared error function.
code: def backward(self, indexes, grad_outputs):
      x0, x1 = self.get_retained_inputs()
      (gy,) = grad_outputs
      gx = gy * 2 * (x0 - x1)
      return gx, -gx
  
file_path: chainer/chainer/functions/loss/squared_error.py
imports: from chainer import function_node
  from chainer import utils
  from chainer.utils import type_check
label_desc: Use image node_id 3 for calling the SquaredError obj's underlying member method code with example usage: obj.backward(indexes, grad_outputs) and returns: gx,  unknown