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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 is_set(self, key):
 """Check to see if the key has been set in any of the data locations. """

        path = key.split(self._key_delimiter)

        lower_case_key = key.lower()
        val = self._find(lower_case_key)

        if val is None:
            source = self._find(path[0].lower())
            if source is not None and isinstance(source, dict):
                val = self._search_dict(source, path[1::])

        return val is not None