Minor imports cleaning (#402)

* code cleaning

* drop unused imports

* optimize imports

pytorch_lightning/logging/comet_logger.py

@@ -1,7 +1,7 @@
-from time import time
-from logging import getLogger
 from os import environ
+
 from comet_ml import Experiment as CometExperiment
+
 from .base import LightningLoggerBase, rank_zero_only
 
 # needed to prevent ImportError and duplicated logs.

pytorch_lightning/logging/mlflow_logger.py

@@ -1,5 +1,5 @@
-from time import time
 from logging import getLogger
+from time import time
 
 import mlflow
 

pytorch_lightning/logging/test_tube_logger.py

@@ -1,16 +1,13 @@
-import os.path
-from copy import copy
+from test_tube import Experiment
 
 from .base import LightningLoggerBase, rank_zero_only
 
-from test_tube import Experiment
-
 
 class TestTubeLogger(LightningLoggerBase):
     __test__ = False
 
     def __init__(
-        self, save_dir, name="default", description=None, debug=False,
+            self, save_dir, name="default", description=None, debug=False,
             version=None, create_git_tag=False
     ):
         super().__init__()