text: try:
      import lz4.block
  except ImportError: # pragma: no cover
      lz4 = None
  
  def decompress_mozLz4(data): # pragma: no cover -- TODO needs mocks instead of just skipping.
      if not lz4:
          raise RuntimeError('Module lz4.block is not detected.')
      assert data[:8] == b'mozLz40\0'
      data = data[8:]
      return lz4.block.decompress(data)
  
  def compress_mozLz4(data): # pragma: no cover -- TODO needs mocks instead of just skipping.
      if not lz4:
          raise RuntimeError('Module lz4.block is not detected.')
      return b'mozLz40\0' + lz4.block.compress(data)
  