remove unused import statements (#845)

To reduce clutter, all unused imports were removed. On the affected
files, imports were also reordered to be PEP8 sorted.

libs/labelFile.py

@@ -6,15 +6,13 @@ try:
 except ImportError:
     from PyQt4.QtGui import QImage
 
-from base64 import b64encode, b64decode
-from libs.pascal_voc_io import PascalVocWriter
-from libs.yolo_io import YOLOWriter
-from libs.pascal_voc_io import XML_EXT
-from libs.create_ml_io import CreateMLWriter
-from libs.create_ml_io import JSON_EXT
-from enum import Enum
 import os.path
-import sys
+from enum import Enum
+
+from libs.create_ml_io import CreateMLWriter
+from libs.pascal_voc_io import PascalVocWriter
+from libs.pascal_voc_io import XML_EXT
+from libs.yolo_io import YOLOWriter
 
 
 class LabelFileFormat(Enum):

libs/settings.py

@@ -1,6 +1,5 @@
-import pickle
 import os
-import sys
+import pickle
 
 
 class Settings(object):

libs/yolo_io.py

@@ -1,11 +1,8 @@
 #!/usr/bin/env python
 # -*- coding: utf8 -*-
-import sys
-import os
-from xml.etree import ElementTree
-from xml.etree.ElementTree import Element, SubElement
-from lxml import etree
 import codecs
+import os
+
 from libs.constants import DEFAULT_ENCODING
 
 TXT_EXT = '.txt'