def __contains__(self, k):
    if not hasattr(self, '_plist'):
      raise PlistNotParsedError

    return k in self._plist
Equivalent of _deleteCustomVar() in GA Javascript client.
dataset/ETHPy150Open google/simian/src/simian/mac/munki/plist.py/ApplePlist.__contains__--crossover with--dataset/ETHPy150Open kra3/py-ga-mob/pyga/requests.py/Tracker.remove_custom_variable