code: def label(self):
      return "digamma"
  
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 1 for calling the DiGamma obj's underlying member method code with example usage: obj.label() and returns: str