public String getTokenName(String literal) {
		Grammar grammar = this;
		while (grammar != null) {
			if (grammar.stringLiteralToTypeMap.containsKey(literal))
				return grammar.getTokenName(grammar.stringLiteralToTypeMap.get(literal));
			grammar = grammar.parent;
		}
		return null;
	}
Return grammar directly imported by this grammar
tool/src/org/antlr/v4/tool/Grammar.java