code: def linspace_pix(self, start=None, stop=None, pixel_step=1, y_vs_x=None):
          
  
          if y_vs_x:
              if start is None:
                  xmin = self.bb_nc1_orig
              else:
                  xmin = start
              if stop is None:
                  xmax = self.bb_nc2_orig
              else:
                  xmax = stop
              num = int(float(xmax-xmin+1)/float(pixel_step)+0.5)
              x = np.linspace(start=xmin, stop=xmax, num=num)
              y = self.poly_funct(x)
          else:
              if start is None:
                  ymin = self.bb_ns1_orig
              else:
                  ymin = start
              if stop is None:
                  ymax = self.bb_ns2_orig
              else:
                  ymax = stop
              num = int(float(ymax-ymin+1)/float(pixel_step)+0.5)
              y = np.linspace(start=ymin, stop=ymax, num=num)
              x = self.poly_funct(y)
  
          return x, y
docs: Return x,y values evaluated with a given pixel step.
  
          The returned values are computed within the corresponding
          bounding box of the line.
  
          Parameters
          ----------
          start : float
              Minimum pixel coordinate to evaluate the independent
              variable.
          stop : float
              Maximum pixel coordinate to evaluate the independent
              variable.
          pixel_step : float
              Pixel step employed to evaluate the independent variable.
          y_vs_x : bool
              If True, the polynomial fit is assumed to be Y vs X.
              Otherwise, X vs Y is employed.
  
          Returns
          -------
          x : 1d numpy array
              X coordinates.
          y : 1d numpy array
              Y coordinates.