docstr: Test if all ``.pyi`` files are properly installed.
docstr_tok: ["Test","if","all","``",".pyi","``","files","are","properly","installed","."]
code: def test_isfile(self):
      """Test if all ``.pyi`` files are properly installed."""
      for file in FILES:
          assert_(os.path.isfile(file))
  
imports: import os
  import sys
  from pathlib import Path
  import numpy
  from numpy.testing import assert_
label_desc: Use image node_id 1 for calling the TestIsFile obj's underlying member method code with example usage: obj.test_isfile() without return types