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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 find_phase(self, obj):
 r""" Find the Phase associated with a given object. Parameters obj : OpenPNM Object Can either be a Physics or Algorithm object Returns ------- An OpenPNM Phase object. Raises ------ If no Phase object can be found, then an Exception is raised. """

        # If received phase, just return self
        if obj._isa('phase'):
            return obj
        # If phase happens to be in settings (i.e. algorithm), look it up
        if 'phase' in obj.settings.keys():
            phase = self.phases()[obj.settings['phase']]
            return phase
        # Otherwise find it using bottom-up approach (i.e. look in phase keys)
        for phase in self.phases().values():
            if ('pore.'+obj.name in phase) or ('throat.'+obj.name in phase):
                return phase
        # If all else fails, throw an exception
        raise Exception('Cannot find a phase associated with '+obj.name)