对于support both a JPEG and WEBP compressed image，我想在网页中包含以下HTML代码：
<picture>
<source srcset="img/awesomeWebPImage.webp" type="image/webp">
<source srcset="img/creakyOldJPEG.jpg" type="image/jpeg">
<img src="img/creakyOldJPEG.jpg" alt="Alt Text!">
</picture>
我一直在使用Python Dominate，它一般对我有用。但是我认为Dominate不支持Picture和Source标签。我可以将HTML添加为raw（）Dominate标记，但是想知道是否有办法让Dominate识别这些标记。
p = picture()
with p:
source(srcset=image.split('.')[0]+'.webp', type="image/webp")
source(srcset=image, type="image/jpeg")
img(src=image, alt=imagealt)
我看到这种错误：
p = picture()
NameError: global name 'picture' is not defined
Dominate用于生成HTML（5）文档。
元素列表在tags.py文件中定义，请参阅GitHub中的存储库：https://github.com/Knio/dominate/blob/master/dominate/tags.py。
但是，picture不是标准标签。
您可以查看包含类似于Dominate的ElementMaker的lxml库，以便轻松构建XML树。见E-Factory。
例如：
>>> from lxml.builder import E
>>> def CLASS(*args): # class is a reserved word in Python
... return {"class":' '.join(args)}
>>> html = page = (
... E.html( # create an Element called "html"
... E.head(
... E.title("This is a sample document")
... ),
... E.body(
... E.h1("Hello!", CLASS("title")),
... E.p("This is a paragraph with ", E.b("bold"), " text in it!"),
... E.p("This is another paragraph, with a", "\n ",
... E.a("link", href="http://www.python.org"), "."),
... E.p("Here are some reserved characters: <spam&egg>."),
... etree.XML("<p>And finally an embedded XHTML fragment.</p>"),
... )
... )
... )
>>> print(etree.tostring(page, pretty_print=True))
<html>
<head>
<title>This is a sample document</title>
</head>
<body>
<h1 class="title">Hello!</h1>
<p>This is a paragraph with <b>bold</b> text in it!</p>
<p>This is another paragraph, with a
<a href="http://www.python.org">link</a>.</p>
<p>Here are some reserved characters: <spam&egg>.</p>
<p>And finally an embedded XHTML fragment.</p>
</body>
</html>