code: def forward_gpu(self, x):
      self.retain_inputs((0,))
      return (
          utils.force_array(
              cuda.cupyx.scipy.special.digamma(x[0]), dtype=x[0].dtype
          ),
      )
  
file_path: chainer/chainer/functions/math/digamma.py
imports: import chainer
  from chainer import backend
  from chainer.backends import cuda
  from chainer import function_node
  from chainer import utils
  from chainer.utils import type_check
label_desc: Use image node_id 4 for calling the DiGamma obj's underlying member method code with example usage: obj.forward_gpu(x) and returns: utils