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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_watched_directory(self, dir_path):
 """ Adds a directory to the watching list. @param dir_path: The path of the directory to be added to the watching list @return: The added directory, or null if failed @since: API v14 """

    req = ApiWatchedDir(self._get_resource_root(), path=dir_path)
    return self._post("watcheddir", ApiWatchedDir, data=req, api_version=14)