code: def y(self, y):
          
          if y is None or y <= 0 or self.log10_ymax - self.log10_ymin == 0:
              return 0
          return (
              self.height - self.height * (log10(y) - self.log10_ymin) /
              (self.log10_ymax - self.log10_ymin)
          )
docs: Project y