(sgml-parse string #!key active: parent:)
Returns a node-list containing a single node that is the root of a grove built by parsing an SGML document or subdocument using the SGML property set. string is the system identifier of the SGML document entity or SGML subdocument entity. active: is a list of strings specifying the names of the active DTD or LPDs. At most one DTD shall be active. If parent: is specified, then the entity to be parsed is an SGML subdocument entity, and the value shall be a singleton node-list in the grove in which the subdocument should be treated as being declared. This uses the default grove plan, which is determined in an application-dependent manner.