AstNode

AstNode:
    | AstStyleSheet
    | AstRuleList
    | AstComment
    | AstAtRule
    | AstRule
    | AstDeclaration
    | AstKeyframesAtRule
    | AstKeyframesRule
    | AstInvalidRule
    | AstInvalidAtRule
    | AstInvalidDeclaration
    | CssVariableToken
    | CssVariableImportTokenType
    | WhitespaceToken