code: def _evaluate_xyz(self,x,y,z=0.):
          
          return -np.pi * self._rhoc_M /(self.n+1.)*self.a**3*self._b*self._c * \
              _potInt(x, y, z, self._a2, self._b2*self._a2, self._c2*self._a2, self.n)
docs: Evaluation of the potential as a function of (x,y,z) in the 
          aligned coordinate frame