How to use the sysrepo.LYD_ANYDATA_CONSTSTRING function in sysrepo

def oper_get_items_cb1(session, module_name, path, request_xpath, request_id, parent, private_data):
    print ("\n\n ========== CALLBACK CALLED TO PROVIDE \"" + path + "\" DATA ==========\n")
    try:
        ctx = session.get_context()
        mod = ctx.get_module(module_name)

        parent.reset(sr.Data_Node(ctx, "/ietf-interfaces:interfaces-state", None, sr.LYD_ANYDATA_CONSTSTRING, 0))
        ifc = sr.Data_Node(parent, mod, "interface")
        name = sr.Data_Node(ifc, mod, "name", "eth100")
        typ = sr.Data_Node(ifc, mod, "type", "iana-if-type:ethernetCsmacd")
        oper_status = sr.Data_Node(ifc, mod, "oper-status", "down")

        ifc.reset(sr.Data_Node(parent, mod, "interface"));
        name.reset(sr.Data_Node(ifc, mod, "name", "eth101"));
        typ.reset(sr.Data_Node(ifc, mod, "type", "iana-if-type:ethernetCsmacd"));
        oper_status.reset(sr.Data_Node(ifc, mod, "oper-status", "up"));

        ifc.reset(sr.Data_Node(parent, mod, "interface"));
        name.reset(sr.Data_Node(ifc, mod, "name", "eth102"));
        typ.reset(sr.Data_Node(ifc, mod, "type", "iana-if-type:ethernetCsmacd"));
        oper_status.reset(sr.Data_Node(ifc, mod, "oper-status", "dormant"));

        ifc.reset(sr.Data_Node(parent, mod, "interface"));