code: def validate_custom_interpreters_list(self):
          
          custom_list = self.get_option('custom_interpreters_list')
          valid_custom_list = []
          for value in custom_list:
              if (osp.isfile(value) and programs.is_python_interpreter(value)
                      and value != get_python_executable()):
                  valid_custom_list.append(value)
          self.set_option('custom_interpreters_list', valid_custom_list)
docs: Check that the used custom interpreters are still valid.