使用svg中pattern标签patternUnits="userSpaceOnUser"属性报错

Question

问题：

使用 svg 中 pattern 标签的 patternUnits 属性时报错。

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svg 代码如下：

<svg width="200" height="200">
        <defs>
            <pattern id="GravelPattern" x="0" y="0" width="100" height="67" viewBox="0 0 100 67" patternUnits="userSpaceOnUser">
                <image x="0" y="0" width="100" height="67" xlink:href="shaliwenli.jpg"></image>
            </pattern>

            <linearGradient id="RedBlackGradient">
                <stop offset="0%" stop-color="#000"></stop>
                <stop offset="100%" stop-color="#f00"></stop>
            </linearGradient>
        </defs>

        <rect x="10" y="20" width="100" height="80" stroke="red" fill="url(#RedBlackGradient)"></rect>
        <circle cx="120" cy="80" r="40" stroke="#00f" stroke-width="8" fill="url(#GravelPattern)"/>
    </svg>

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浏览器控制台报错信息：

Error: <pattern> attribute patternUnits: Unrecognized enumerated value, "userSpaceOnUser".