code: def __flush(self):
          
          try:
              self.__flush_buffer()
  
              self._file['md5'] = self._file["md5"].hexdigest()
              self._file["length"] = self._position
              self._file["uploadDate"] = datetime.datetime.utcnow()
  
              return self._coll.files.insert_one(self._file)
          except DuplicateKeyError:
              self._raise_file_exists(self._id)
docs: Flush the file to the database.