public void importTokensFromTokensFile() {
		String vocab = getOptionString("tokenVocab");
		if ( vocab!=null ) {
			TokenVocabParser vparser = new TokenVocabParser(this);
			Map<String,Integer> tokens = vparser.load();
			tool.log("grammar", "tokens=" + tokens);
			for (String t : tokens.keySet()) {
				if ( t.charAt(0)=='\'' ) defineStringLiteral(t, tokens.get(t));
				else defineTokenName(t, tokens.get(t));
			}
		}
	}
Return a new unique integer in the channel value space.
tool/src/org/antlr/v4/tool/Grammar.java