def _R2deriv(self,R,phi=0.,t=0.):
        """
        NAME:
           _R2deriv
        PURPOSE:
           evaluate the second radial derivative
        INPUT:
           R
           phi
           t
        OUTPUT:
           d2phi/dR2
        HISTORY:
           2016-06-02 - Written - Bovy (UofT)
        """
        return self._Pot.R2deriv(R,0.,phi=phi,t=t,use_physical=False)
def _R2deriv ( self , R , phi = 0. , t = 0. ) : return self . _Pot . R2deriv ( R , 0. , phi = phi , t = t , use_physical = False )
NAME:
           _R2deriv
        PURPOSE:
           evaluate the second radial derivative
        INPUT:
           R
           phi
           t
        OUTPUT:
           d2phi/dR2
        HISTORY:
           2016-06-02 - Written - Bovy (UofT)