code: def get_pltpat(self, plt_ext="svg"):
          
          if self.ntplt.desc == "":
              return ".".join(["{BASE}", plt_ext])
          return "".join(["{BASE}_", self.ntplt.desc, ".", plt_ext])
docs: Return png pattern: {BASE}.png {BASE}_pruned.png {BASE}_upper_pruned.png