class type ['a Pxp_document.node #Pxp_document.extension as 'a] index = object .. end
The type of indexes over the ID attributes of the elements. This type
is the minimum requirement needed by the parser to create such an index.
method add : string -> 'a Pxp_document.node -> unit
Add the passed node to the index. If there is already an ID with
the passed string value, the exception
Pxp_tree_parser.ID_not_unique
can be raised. However, index implementations are free to also accept
several identical IDs, although this does not comply to the standard.
method find : string -> 'a Pxp_document.node
Finds the node with the passed ID value, or raises Not_found
