Css classes
    A should have a red background with styling from class.
    
    graph LR;
        A-->B[AAABBB];
        B-->D;
        class A cssClass;
    
    A should have a red background with styling from style definition.
    
    graph LR;
        A-->B[AAABBB];
        B-->D;
        style A fill:#FF0000,stroke:#FFFF00,stroke-width:4px;
    
    A should have orange background with styling from local class definition definition.
    
    graph LR;
        A-->B[AAABBB];
        B-->D;
        classDef orange fill:#f96,stroke:#333,stroke-width:4px;
        class A orange;
        linkStyle 0 stroke:#ff3,stroke-width:4px;
        classDef default fill:#f9f,stroke:#333,stroke-width:4px;