StyleSheet
  RuleSet
    Selector
      SimpleSelector
        IdLiteral : #xxx
    PropertyDeclaration
      Property : filter
      Expr
        Term
          FunctionCall : alpha
            Expr
              Term
                IdentLiteral : opacity
              Operation : EQUAL
              Term
                QuantityLiteral : 50
    EmptyDeclaration
  RuleSet
    Selector
      SimpleSelector
        IdentLiteral : p
    PropertyDeclaration
      Property : margin
      Expr
        Term : NEGATION
          QuantityLiteral : 3px
        Operation : NONE
        Term : NEGATION
          QuantityLiteral : 3px
  RuleSet
    Selector
      SimpleSelector
        IdentLiteral : p
    PropertyDeclaration
      Property : margin
      Expr
        Term : NEGATION
          QuantityLiteral : 3px
        Operation : NONE
        Term
          QuantityLiteral : 3px