code: def get(self, pid, record, key, version_id, **kwargs):
          
          try:
              obj = record.files[str(key)].get_version(version_id=version_id)
              return self.make_response(
                  obj=obj or abort(404), pid=pid, record=record)
          except KeyError:
              abort(404)
docs: Get file.
  
          Permission required: `read_permission_factory`.
  
          :param pid: Pid object (from url).
          :param record: Record object resolved from the pid.
          :param key: Unique identifier for the file in the deposit.
          :param version_id: File version. Optional. If no version is provided,
              the last version is retrieved.
          :returns: the file content.