class_docstr: Select index of an array element from a given axis.
code: def forward(self, x):
      xp = backend.get_array_module(*x)
      return (xp.asarray(self._fwd(x[0], xp)),)
  
imports: import numpy
  import six
  from chainer import backend
  from chainer import function_node
  import chainer.functions
  import chainer.utils
  from chainer.utils import type_check
  import chainerx
label_desc: Use image node_id 4 for calling the IndexSelectorBase obj's underlying member method code with example usage: obj.forward(x) and returns: xp