docs: def _compute_checksum(self, stream, size=None, chunk_size=None,
                            progress_callback=None, **kwargs):
          """Get helper method to compute checksum from a stream.
  
          Naive implementation that can be overwritten by subclasses in order to
          provide more efficient implementation.
          """
          if progress_callback and size:
              progress_callback = partial(progress_callback, size)
          else:
              progress_callback = None
  
          try:
              algo, m = self._init_hash()
              return compute_checksum(
                  stream, algo, m,
                  chunk_size=chunk_size,
                  progress_callback=progress_callback,
                  **kwargs
              )
          except Exception as e:
              raise StorageError(
                  'Could not compute checksum of file: {0}'.format(e))