You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: datastream.rb
    path of file: ./repos/truffleruby/bench/chunky_png/chunky_png/lib/chunky_png
    
    the code of the file until where you have to start completion: module ChunkyPNG

  # The Datastream class represents a PNG formatted datastream. It supports
  # both reading from and writing to strings, streams and files.
  #
  # A PNG datastream begins with the PNG signature, and than contains multiple
  # chunks, starting with a header (IHDR) chunk and finishing with 
    
      def from_io(io)
        verify_signature!(io)

        ds = self.new
        until io.eof?
          chunk = ChunkyPNG::Chunk.read(io)
          case chunk
            when ChunkyPNG::Chunk::Header;       ds.header_chunk = chunk
            when ChunkyPNG::Chunk::Palette;      ds.palette_chunk = chunk
            when ChunkyPNG::Chunk::Transparency; ds.transparency_chunk = chunk
            when ChunkyPNG::Chunk::ImageData;    ds.data_chunks << chunk
            when ChunkyPNG::Chunk::End;          ds.end_chunk = chunk
            else ds.other_chunks << chunk
          end