docs: def resolve_dependency(dep):
    """
    Attempts to find the #Dependency on the system. Returns the filename of the
    native library or None if it can not be found.
    """
  
    for dirname in os.getenv('PATH', '').split(os.pathsep):
      filename = os.path.join(dirname, dep.name)
      if os.path.isfile(filename):
        return _get_long_path_name(filename)
    return None