class_docstr: git-annex special-remote frontend for DataLad's downloader facility
      
code: def checkpresent(self, key):
      resp = None
      for url in self.gen_URLS(key):
          # somewhat duplicate of CHECKURL
          try:
              status = self._providers.get_status(url)
              if status:  # TODO:  anything specific to check???
                  return True
              # TODO:  for CHECKPRESENT-FAILURE we somehow need to figure out
              # that we can connect to that server but that specific url is
              # N/A, probably check the connection etc
          except TargetFileAbsent as exc:
              ce = CapturedException(exc)
              self.message(
                  "Target url %s file seems to be missing: %s"
                  % (url, ce)
              )
              if not resp:
                  # if it is already marked as UNKNOWN -- let it stay that
                  # way but if not -- we might as well say that we can no
                  # longer access it
                  return False
          except Exception as exc:
              ce = CapturedException(exc)
              self.message(
                  "Failed to check status of url %s: %s" % (url, ce)
              )
      if resp is None:
          raise RemoteError(
              f"Could not determine presence of key {key}"
          )
      else:
          return False
  
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 4 for calling the DataladAnnexCustomRemote obj's underlying member method code with example usage: obj.checkpresent(key) and returns: False, True, False