text: # main.py
  import sys
  
  # we import our custom importer module
  import importer
  
  # import module1.py using our own importer
  module1 = importer.import_('module1', 'module1_source.py', '.')
  
  # we can see that module1 is in sys.modules
  print('sys says:', sys.modules.get('module1', 'module1 not found'))
  
  # and we can now import this module "normally" from other locations
  # such as module2.py
  import module2
  module2.hello()
  
  # notice how the first time we imported (using import_) module1, it "ran" (printed running module1).
  # but the second time we imported it (in module2) it did not
  # that's because Python recovered module1 from cache, and did not rebuild it
  