code: def get_all_sizes_checksums():
    
    sizes_checksums = {}
    for path in _checksum_paths().values():
      data = _get_sizes_checksums(path)
      for url, size_checksum in data.items():
        if (url in sizes_checksums and
            sizes_checksums[url] != size_checksum):
          raise AssertionError(
              'URL %s is registered with 2+ distinct size/checksum tuples.' % url)
      sizes_checksums.update(data)
    return sizes_checksums
docs: Returns dict associating URL to (size, sha256).