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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_format(self, key, value=None):
 """Add an entry to format The record's calls ``data[key]`` will be set to ``value`` if not yet set and value is not ``None``. If key is already in FORMAT then nothing is done. """

        if key in self.FORMAT:
            return
        self.FORMAT.append(key)
        if value is not None:
            for call in self:
                call.data.setdefault(key, value)