class_docstr: Similar to CombinedLoaderIterator in Lightning, but in a concat manner.
docstr: Fetches the next batch from multiple data loaders,
  by looking for the first iterator that isn't exhausted yet.
code: def __next__(self) -> Any:
      """Fetches the next batch from multiple data loaders,
      by looking for the first iterator that isn't exhausted yet.
      """
      if not len(self.loader_iters) == len(self.loaders):
          raise RuntimeError(
              "loader_iters must have the same length as loaders."
          )
      for i, (loader_name, iterator) in enumerate(
          self.loader_iters.items()
      ):
          try:
              return (self.request_next_batch(iterator), loader_name)
          except StopIteration:
              if i + 1 == len(self.loader_iters):
                  raise
  
file_path: nni/nni/nas/oneshot/pytorch/_dataloader_legacy.py
imports: from __future__ import annotations
  from typing import Any
  from pytorch_lightning.trainer.supporters import CombinedLoader, CombinedLoaderIterator
label_desc: Use image node_id 1 for calling the ConcatLoaderIterator obj's underlying member method code with example usage: obj.__next__() and returns: self,  loader_name