fix(agent): init .py missing DPM2/DPM++ exports.

Author: chaircbot

iddm/model/samples/__init__.py

@@ -24,3 +24,5 @@
 from .ddim import DDIMDiffusion
 from .ddpm import DDPMDiffusion
 from .plms import PLMSDiffusion
+from .dpm2 import DPM2Diffusion
+from .dpmpp import DPMPlusPlusDiffusion