<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _add_finder(importer, finder):
 """Register a new pkg_resources path finder that does not replace the existing finder."""


  existing_finder = _get_finder(importer)

  if not existing_finder:
    pkg_resources.register_finder(importer, finder)
  else:
    pkg_resources.register_finder(importer, ChainedFinder.of(existing_finder, finder))