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