NameError: name 'ZR' is not defined

[CP32]

In the pairinggroup.py, it has the code " from charm.core.math.pairing import pairing,pc_element,ZR,G1,G2,GT,init,pair,hashPair,H,random,serialize,deserialize,ismember,order ". However I can't find the ZR,G1...... How can I solve this problem? Have I miss some files?