code: def forward(self, inputs):
      (x,) = inputs
      self._in_shape = x.shape
      y = x.diagonal(
          offset=self.offset, axis1=self.axis1, axis2=self.axis2
      )
      return (y,)
  
file_path: chainer/chainer/functions/array/diagonal.py
imports: import numpy
  from chainer import backend
  from chainer import function_node
  from chainer.utils import type_check
label_desc: Use image node_id 3 for calling the Diagonal obj's underlying member method code with example usage: obj.forward(inputs) and returns: y