def _mdens_deriv(self,m):
        """Derivative of the density as a function of m"""
        return -2.*self.a2**2*(self.a+2.*m)/m**3/(self.a+m)**3
def _mdens_deriv ( self , m ) : return - 2. * self . a2 ** 2 * ( self . a + 2. * m ) / m ** 3 / ( self . a + m ) ** 3
Derivative of the density as a function of m