code: def _from_str_subscript(subscript):
      # subscript should be lower case (a-z)
      return [
          (Ellipsis if char == "@" else ord(char) - ord("a"))
          for char in subscript.replace("...", "@")
      ]
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer.functions.math import einsum
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer import utils
label_desc: Use image node_id 2 for calling a global function with example usage: _from_str_subscript(subscript) and returns: unknown