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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 merge_extra_options(self, needs_info):
 """Add any extra options introduced via options_ext to needs_info"""

        extra_keys = set(self.options.keys()).difference(set(needs_info.keys()))
        for key in extra_keys:
            needs_info[key] = self.options[key]

        # Finally add all not used extra options with empty value to need_info.
        # Needed for filters, which need to access these empty/not used options.
        for key in self.option_spec:
            if key not in needs_info.keys():
                needs_info[key] = ""

        return extra_keys