[pplm] split classif head into its own file

examples/pplm/run_pplm.py

@@ -33,10 +33,10 @@ import torch.nn.functional as F
 from torch.autograd import Variable
 from tqdm import trange
 
-from examples.run_pplm_discrim_train import ClassificationHead
 from transformers import GPT2Tokenizer
 from transformers.file_utils import cached_path
 from transformers.modeling_gpt2 import GPT2LMHeadModel
+from pplm_classification_head import ClassificationHead
 
 PPLM_BOW = 1
 PPLM_DISCRIM = 2