code: def R2deriv(self,R,phi=0.,t=0.):
          
          try:
              return self._amp*self._R2deriv(R,phi=phi,t=t)
          except AttributeError: #pragma: no cover
              raise PotentialError("'_R2deriv' function not implemented for this potential")
docs: NAME:
  
             R2deriv
  
          PURPOSE:
  
             evaluate the second radial derivative
  
          INPUT:
  
             R - Cylindrical radius (can be Quantity)
  
             phi= azimuth (optional; can be Quantity)
  
             t= time (optional; can be Quantity)
  
          OUTPUT:
  
             d2phi/dR2
  
          HISTORY:
  
             2011-10-09 - Written - Bovy (IAS)