The internal subset as a string, or null if there is none.
This is does not contain the delimiting square brackets.
Note:
The actual content returned depends on how much information is available
to the implementation. This may vary depending on various parameters,
including the XML processor used to build the document.
The internal subset as a string, or null if there is none. This is does not contain the delimiting square brackets.
Note: The actual content returned depends on how much information is available to the implementation. This may vary depending on various parameters, including the XML processor used to build the document.