code: def test_hash_ecfp_pair(self):
      for power in (2, 16, 64):
          for _ in range(10):
              string1 = random_string(10)
              string2 = random_string(10)
              pair_hash = hash_utils.hash_ecfp_pair(
                  (string1, string2), power
              )
              self.assertIsInstance(pair_hash, int)
              self.assertLess(pair_hash, 2**power)
              self.assertGreaterEqual(pair_hash, 0)
  
file_path: deepchem/deepchem/utils/test/test_hash_utils.py
imports: import unittest
  import numpy
  from deepchem.utils import hash_utils
label_desc: Use image node_id 2 for calling the TestHashUtils obj's underlying member method code with example usage: obj.test_hash_ecfp_pair() without return types