Fix import error in deepspeed_to_megatron.py (#455)

Previously, `deepspeed_to_megatron.py` would raise an import error
due to the relative import.

This commit fixes this issue by changing from the relative import
to the absolute import like in `deepspeed_to_transformers.py`.

Author: hotsuyuki

tools/convert_checkpoint/deepspeed_to_megatron.py

@@ -4,7 +4,7 @@
 import os
 import torch
 from collections import OrderedDict
-from .deepspeed_checkpoint import ARGS_KEY, DeepSpeedCheckpoint
+from deepspeed_checkpoint import ARGS_KEY, DeepSpeedCheckpoint
 
 MODEL_KEY = 'model'
 ARGS_KEY = 'args'
@@ -92,7 +92,7 @@ def _create_rank_checkpoint(ds_checkpoint, tp_index, pp_index, for_release=False
         if pp_index == 0:
             meg_embedding_sd.update(nested_embedding_sd)
 
-        if pp_index == ds_checkpoint.pp_degree -1:
+        if pp_index == ds_checkpoint.pp_degree - 1:
             for key, value in embedding_sd.items():
                 if key.startswith(WORD_EMBEDDINGS_KEY):
                     fields = key.split('.')
@@ -111,7 +111,7 @@ def _create_rank_checkpoint(ds_checkpoint, tp_index, pp_index, for_release=False
     if pp_index == 0:
         checkpoint_sd[MODEL_KEY][LANGUGAGE_MODEL_KEY][EMBEDDING_KEY] = meg_embedding_sd
     checkpoint_sd[MODEL_KEY][LANGUGAGE_MODEL_KEY][ENCODER_KEY] = meg_encoder_sd
-    if pp_index == ds_checkpoint.pp_degree -1:
+    if pp_index == ds_checkpoint.pp_degree - 1:
         checkpoint_sd[MODEL_KEY][WORD_EMBEDDINGS_FOR_HEAD_KEY] = meg_embedding_for_head_sd
 
     checkpoint_sd[ARGS_KEY] = ds_checkpoint.get_args()