code: def show_setup(self):
          
          shell = os.getenv('SHELL')
          if not shell:
              raise SystemError("No $SHELL env var found")
          shell = os.path.basename(shell)
          if shell not in self.script_body:
              raise SystemError("Unsupported shell: %s" % shell)
          tplvars = {
              "prog": '-'.join(self.prog.split()[:-1]),
              "shell": shell,
              "name": self.name
          }
          print(self.trim(self.script_header % tplvars))
          print(self.trim(self.script_body[shell] % tplvars))
          print(self.trim(self.script_footer % tplvars))
docs: Provide a helper script for the user to setup completion.