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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_tnames(self):
 """Get the name of the time coordinate of the objects in this list"""

        tnames = set()
        for arr in self:
            if isinstance(arr, InteractiveList):
                tnames.update(arr.get_tnames())
            else:
                tnames.add(arr.psy.decoder.get_tname(
                    next(arr.psy.iter_base_variables), arr.coords))
        return tnames - {None}