code: func (p *Parser) Ogdl() {
  	n, u := p.Space()
  	if u == 0 {
  		return // Error
  	}
  	for i := n; i > 0; i-- {
  		p.UnreadByte()
  	}
  	p.tree(n, false)
  }
docs: // Ogdl is the main function for parsing OGDL text.
  //
  // An OGDL stream is a sequence of lines (a block
  // of text or a quoted string can span multiple lines
  // but is still parsed by Line())
  //
  //     Graph ::= Line* End