Do not use a mutable argument by default

Author: xcodinas

barcode/__init__.py

@@ -49,7 +49,8 @@
 PROVIDED_BARCODES.sort()
 
 
-def get(name, code=None, writer=None, options={}):
+def get(name, code=None, writer=None, options=None):
+    options = options or {}
     try:
         barcode = __BARCODE_MAP[name.lower()]
     except KeyError: