Gets the value for nested `key`, returns `default` if key does not exist. Names with underscores will be considered as one key. Args: key: str of the form `([A-Za-z_][A-Za-z0-9_]*)(.[A-Za-z_][A-Za-z0-9_]*)*.`. default: Optional default value, defaults to None. Retu
(self, key: str, default: Optional[Any] = None)
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