Optional children for the tag. Must be either
objects of class XiMpLe.node or character strings, which
are treated as simple text values. If this is empty, the
tag will be treated as an empty tag. To force a closing
tag, supply an empty string, i.
attrs
An optional named list of attributes.
namespace
Currently ignored.
namespaceDefinitions
Currently ignored.
.children
Alternative way of specifying children,
if you have them already as a list.