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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 get_extra_kwargs(self):
 """ Return a dictionary mapping field names to a dictionary of additional keyword arguments. """

        extra_kwargs = getattr(self.Meta, 'extra_kwargs', {})

        read_only_fields = getattr(self.Meta, 'read_only_fields', None)
        if read_only_fields is not None:
            for field_name in read_only_fields:
                kwargs = extra_kwargs.get(field_name, {})
                kwargs['read_only'] = True
                extra_kwargs[field_name] = kwargs

        return extra_kwargs