Get an immutable copy of this Location object. By default Location objects may be mutable, so they
should not be saved for later use. The result of this operation holds the same location information,
but in an immutable form.
Get an iterator over all the properties available. The values returned by the iterator
will be of type String, and each string can be supplied as input to the getProperty()
method to retrieve the value of the property.
Get the public ID of the module containing the instruction. This method
is provided to satisfy the SourceLocator interface. However, the public ID is
not maintained by Saxon, and the method always returns null