class_docstr: git-annex special-remote frontend for DataLad's downloader facility
      
code: def transfer_retrieve(self, key, file):
      urls = []
      error_causes = []
      # TODO: priorities etc depending on previous experience or settings
      for url in self.gen_URLS(key):
          urls.append(url)
          try:
              downloaded_path = self._providers.download(
                  url, path=file, overwrite=True
              )
              assert downloaded_path == file
              return
          except Exception as exc:
              ce = CapturedException(exc)
              debug_msg = (
                  f"Failed to download {url} for key {key}: "
                  f"{ce.format_with_cause()}"
              )
              self.message(debug_msg)
              error_causes.append(ce.format_with_cause())
  
      error_msg = (
          f"Failed to download from any of {len(urls)} locations"
      )
      if error_causes:
          error_msg += f" {unique(error_causes)}"
      raise RemoteError(error_msg)
  
file_path: datalad/datalad/customremotes/datalad.py
imports: import logging
  from urllib.parse import urlparse
  from datalad.downloaders.providers import Providers
  from datalad.support.exceptions import CapturedException, TargetFileAbsent
  from datalad.utils import unique
  from datalad.customremotes import RemoteError
  from datalad.customremotes.base import AnnexCustomRemote
  from datalad.customremotes.main import main
label_desc: Use image node_id 2 for calling the DataladAnnexCustomRemote obj's underlying member method code with example usage: obj.transfer_retrieve(key, file) without return types