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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_capacity(self, legacy=None):
 """Get capacity of all facilities. :param legacy: Indicate set of server types to include in response Validation of `legacy` is left to the packet api to avoid going out of date if any new value is introduced. The currently known values are: - only (current default, will be switched "soon") - include - exclude (soon to be default) """

        params = None
        if legacy:
            params = {'legacy': legacy}

        return self.call_api('/capacity', params=params)['capacity']