code: def test_hashing(self):
      ids = ["1", "2", "4", "5"]
      salt = str(uuid4())
      hex_string = to_hex_string(ids, salt)
      hex_string
  
imports: import unittest
  from uuid import uuid4
  from bigdl.ppml.fl.psi.utils import *
  from bigdl.ppml.fl.utils import FLTest
label_desc: Use image node_id 1 for calling the TestHashing obj's underlying member method code with example usage: obj.test_hashing() without return types