code: def test_live_issue_117():
      assert bin_to_gray("0100") == "0110"
      assert bin_to_gray("0101") == "0111"
      for bits in ("0100", "0101"):
          assert gray_to_bin(bin_to_gray(bits)) == bits
  
imports: from sympy.combinatorics.graycode import GrayCode, bin_to_gray, random_bitstring, get_subset_from_bitstring, graycode_subsets, gray_to_bin
  from sympy.testing.pytest import raises
label_desc: Use image node_id 2 for calling a global function with example usage: test_live_issue_117() without return types