Inherit attributes to single child

===

<svg xmlns="http://www.w3.org/2000/svg">
    <g>
        <g attr1="val1">
            <path d="..."/>
        </g>
    </g>
    <g attr1="val1">
        <g attr2="val2">
            <path d="..."/>
        </g>
    </g>
    <g attr1="val1">
        <g>
            <path d="..."/>
        </g>
        <path d="..."/>
    </g>
    <g attr1="val1">
        <g attr2="val2">
            <path d="..."/>
        </g>
        <path d="..."/>
    </g>
</svg>

@@@

<svg xmlns="http://www.w3.org/2000/svg">
    <path d="..." attr1="val1"/>
    <path d="..." attr2="val2" attr1="val1"/>
    <g attr1="val1">
        <path d="..."/>
        <path d="..."/>
    </g>
    <g attr1="val1">
        <path d="..." attr2="val2"/>
        <path d="..."/>
    </g>
</svg>