code: def to_linear(self, index=None):
          
          if index is None:
              n = len(self.index)-1
              index = [self.index[i]*(1.-i/(n-1.))+self.index[i+1]*i/(n-1.) for
                       i in range(n)]
  
          colors = [self.rgba_floats_tuple(x) for x in index]
          return LinearColormap(colors, index=index,
                                vmin=self.vmin, vmax=self.vmax)
docs: Transforms the StepColormap into a LinearColormap.
  
          Parameters
          ----------
          index : list of floats, default None
                  The values corresponding to each color in the output colormap.
                  It has to be sorted.
                  If None, a regular grid between `vmin` and `vmax` is created.