gobbleGroup() {
		this.index++;
		let nodes = this.gobbleExpressions(Jsep.CPAREN_CODE);
		if (this.code === Jsep.CPAREN_CODE) {
			this.index++;
			if (nodes.length === 1) {
				return nodes[0];
			}
			else if (!nodes.length) {
				return false;
			}
			else {
				return {
					type: Jsep.SEQUENCE_EXP,
					expressions: nodes,
				};
			}
		}
		else {
			this.throwError('Unclosed (');
		}
	}
Responsible for parsing a group of things within parentheses `()`
that have no identifier in front (so not a function call)
This function assumes that it needs to gobble the opening parenthesis
and then tries to gobble everything within that parenthesis, assuming
that the next thing it should see is the close parenthesis. If not,
then the expression probably doesn't have a `)`
@returns {boolean|jsep.Expression}