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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 LoadFromString(cls, yaml_doc):
 """Creates an AdWordsClient with information stored in a yaml string. Args: yaml_doc: The yaml string containing the cached AdWords data. Returns: An AdWordsClient initialized with the values cached in the string. Raises: A GoogleAdsValueError if the given yaml string does not contain the information necessary to instantiate a client object - either a required key was missing or an OAuth2 key was missing. """

    return cls(**googleads.common.LoadFromString(
        yaml_doc, cls._YAML_KEY, cls._REQUIRED_INIT_VALUES,
        cls._OPTIONAL_INIT_VALUES))