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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 _gap_progenitor_setup(self):
 """Setup an Orbit instance that's the progenitor integrated backwards"""

        self._gap_progenitor= self._progenitor().flip() # new orbit, flip velocities
        # Make sure we do not use physical coordinates
        self._gap_progenitor.turn_physical_off()
        # Now integrate backward in time until tdisrupt
        ts= numpy.linspace(0.,self._tdisrupt,1001)
        self._gap_progenitor.integrate(ts,self._pot)
        # Flip its velocities, should really write a function for this
        self._gap_progenitor._orb.orbit[:,1]= -self._gap_progenitor._orb.orbit[:,1]
        self._gap_progenitor._orb.orbit[:,2]= -self._gap_progenitor._orb.orbit[:,2]
        self._gap_progenitor._orb.orbit[:,4]= -self._gap_progenitor._orb.orbit[:,4]
        return None