feature_simple : VAR comparator NUMBER VAR
                          | VAR comparator NUMBER
                          | VAR comparator LBRACK string_list RBRACK
                          | VAR comparator STRING

def p_feature_simple(self, t):
        """feature_simple : VAR comparator NUMBER VAR
                          | VAR comparator NUMBER
                          | VAR comparator LBRACK string_list RBRACK
                          | VAR comparator STRING"""

        if len(t) == 6:
            t[0] = Feature(t[1], t[2], t[4], line=t.lineno(1))
        elif len(t) == 5:
            t[0] = Feature(t[1], t[2], t[3], unit=t[4], line=t.lineno(1))
        elif len(t) == 4:
            t[0] = Feature(t[1], t[2], t[3], line=t.lineno(1))