startTag
Writes a start tag with the given namespace and name. If there is no prefix defined for the given namespace, a prefix will be defined automatically. The explicit prefixes for namespaces can be established by calling namespacePrefix immediately before this method. If namespace is null no namespace prefix is printed but just name. If namespace is empty string then serializer will make sure that default empty namespace is declared (in XML 1.0 xmlns='') or throw IllegalStateException if default namespace is already bound to non-empty string.