code: def _document_root(self, fully_qualified=True):
          
          nsmap = {"xsi": utils.NAMESPACES["xsi"], "xlink": utils.NAMESPACES["xlink"]}
          if fully_qualified:
              nsmap["mets"] = utils.NAMESPACES["mets"]
          else:
              nsmap[None] = utils.NAMESPACES["mets"]
          attrib = {
              "{}schemaLocation".format(utils.lxmlns("xsi")): utils.SCHEMA_LOCATIONS
          }
          if self.objid:
              attrib["OBJID"] = self.objid
          return etree.Element(utils.lxmlns("mets") + "mets", nsmap=nsmap, attrib=attrib)
docs: Return the mets Element for the document root.