new_contents: import sys
  from mgz import header, body
  
  if __name__ == "__main__":
      # For each input filename
      for arg in sys.argv[1:]:
          with open(arg, 'rb') as f:
              # Remember end of file
              f.seek(0, 2)
              eof = f.tell()
              f.seek(0, 0)
              # Parse the header
              h = header.parse_stream(f)
              # Parse the body
              while True:
                  # Parse a body operation
                  o = body.operation.parse_stream(f)
                  # Stop if all data has been read
                  if f.tell() == eof:
                      break
  
subject: add basic usage example