#mixed_content  // f.c.MixedContent
    #assign  // f.c.Assignment
        - assignment target: "xs"  // String
        - assignment operator: "="  // String
        - assignment source: [...]  // f.c.ListLiteral
        - variable scope: "1"  // Integer
        - namespace: null  // Null
    #text  // f.c.TextBlock
        - content: "\n"  // String
    #list  // f.c.IteratorBlock
        - list source: x  // f.c.Identifier
        - target loop variable: "xs"  // String
        #text  // f.c.TextBlock
            - content: "    "  // String
        ${...}  // f.c.DollarVariable
            - content: x  // f.c.Identifier
        #text  // f.c.TextBlock
            - content: "\n"  // String
    #text  // f.c.TextBlock
        - content: "\n"  // String
    #assign  // f.c.Assignment
        - assignment target: "a"  // String
        - assignment operator: "="  // String
        - assignment source: 1  // f.c.NumberLiteral
        - variable scope: "1"  // Integer
        - namespace: null  // Null
    #assign  // f.c.Assignment
        - assignment target: "b"  // String
        - assignment operator: "="  // String
        - assignment source: 1  // f.c.NumberLiteral
        - variable scope: "1"  // Integer
        - namespace: null  // Null
    #text  // f.c.TextBlock
        - content: "\n"  // String
    @  // f.c.UnifiedCall
        - callee: b  // f.c.Identifier
        #text  // f.c.TextBlock
            - content: "    x\n"  // String
    #text  // f.c.TextBlock
        - content: "\n"  // String
    @  // f.c.UnifiedCall
        - callee: c  // f.c.Identifier
    #text  // f.c.TextBlock
        - content: "\n"  // String
    @  // f.c.UnifiedCall
        - callee: d  // f.c.Identifier
    #text  // f.c.TextBlock
        - content: "\na\n"  // String
    #--...--  // f.c.Comment
        - content: " comment "  // String
    #text  // f.c.TextBlock
        - content: "b"  // String
