code: def resolve_loader(self, meta: ProgramDescription):
          
          if not meta.loader:
              meta.loader = 'single' if meta.path else 'separate'
  
          for loader_cls in self._loaders:
              if loader_cls.name == meta.loader:
                  meta.loader_cls = loader_cls
                  break
          else:
              raise ImproperlyConfigured(
                  (
                      "Program {} has no loader class registered."
                      "Check PROGRAM_LOADERS or PROGRAM_DIRS"
                  ).format(meta.path)
              )
docs: Resolve program loader