code: def gkk_filepath(self):
          
          if self.gkk_node is None: return "GKK_FILE_DOES_NOT_EXIST"
          if isinstance(self.gkk_node, FileNode): return self.gkk_node.filepath
  
          path = self.gkk_node.outdir.has_abiext("GKK")
          return path if path else "GKK_FILE_DOES_NOT_EXIST"
docs: Returns (at runtime) the absolute path of the input GKK file.