code: def _plotxw(self,*args,**kwargs): #pragma: no cover
          
          xw= self.xw()
          #BOVY: CHECK THAT THIS IS CORRECT
          plot.bovy_plot(2.*m.pi*nu.fft.fftfreq(len(self.t),
                                                d=(self.t[1]-self.t[0]))\
                             [0:len(xw)],
                         xw,*args,**kwargs)
docs: NAME:
             plotxw
          PURPOSE:
             plot the spectrum of x
          INPUT:
             bovy_plot.bovy_plot args and kwargs
          OUTPUT:
             x(t)
          HISTORY:
             2010-09-21 - Written - Bovy (NYU)