code: def test_sigmoid():
      a = C.input_variable(
          (), dtype=np.float16, needs_gradient=True, name="a"
      )
      s = C.sigmoid(a)
      result = s.eval([[0]])
      grad = s.grad([[0]])
      assert np.array_equal(
          result, np.asarray([0.5]).astype(np.float16)
      )
      assert np.array_equal(grad, np.asarray([0.25]).astype(np.float16))
  
file_path: CNTK/bindings/python/cntk/ops/tests/fp16_test.py
imports: from __future__ import division
  import numpy
  import pytest
  from .ops_test_utils import _test_binary_op, AA, PRECISION_TO_TYPE, unittest_helper
  import cntk
label_desc: Use image node_id 1 for calling a global function with example usage: test_sigmoid() without return types