code: def _merge_relative_path(dst_path, rel_path):
    
    # Convert rel_path to be relative and normalize it to remove ".", "..", "//",
    # which are valid directories in fileystems like "gs://".
    norm_rel_path = os.path.normpath(rel_path.lstrip("/"))
  
    if norm_rel_path == ".":
      return dst_path
  
    # Check that the norm rel path does not starts with "..".
    if norm_rel_path.startswith(".."):
      raise ValueError("Relative path %r is invalid." % rel_path)
  
    merged = os.path.join(dst_path, norm_rel_path)
  
    # After merging verify that the merged path keeps the original dst_path.
    if not merged.startswith(dst_path):
      raise ValueError("Relative path %r is invalid. Failed to merge with %r." % (
          rel_path, dst_path))
    return merged
docs: Merge a relative tar file to a destination (which can be "gs://...").