classThis class is an implementation of[< clone : 'a; node : 'a node;namespace_element_impl :
set_node : 'a node -> unit; .. >
as 'a]'a ->['a]node
node which
   realizes element nodes. In contrast to element_impl, this class
   also implements the namespace methods.
 This class has an extended definition of the create_element method.
 It accepts element names of the form "normprefix:localname" where
 normprefix must be a prefix managed by the namespace_manager. Note
 that create_element does not itself normalize prefixes; it is expected
 that the prefixes are already normalized. 
 In addition to calling create_element, one can set the namespace scope
 after creation (set_namespace_scope) to save the mapping of unprocessed
 namespace prefixes to normalized prefixes. This is voluntary.
 Such nodes have the node type T_element "normprefix:localname".
 This class implements the namespace methods.