def __add_files(self, pyfiles, root, files):
        """ if files match, appends them to pyfiles. used by os.path.walk fcn """
        for fname in files:
            if self.__is_valid_py_file(fname):
                name_without_base_dir = self.__unixify(os.path.join(root, fname))
                pyfiles.append(name_without_base_dir)
 if files match, appends them to pyfiles. used by os.path.walk fcn 
debugger/src/_pydev_runfiles/pydev_runfiles.py