Fix #379

twint/storage/write.py

@@ -48,10 +48,12 @@ def createDirIfMissing(dirname):
 
 def Csv(obj, config):
     _obj_type = obj.__class__.__name__
+    if _obj_type == "str":
+        _obj_type = "username"
     fieldnames, row = struct(obj, config.Custom[_obj_type], _obj_type)
-
+    
     base = addExt(config.Output, _obj_type, "csv")
-
+    
     if not (os.path.exists(base)):
         with open(base, "w", newline='', encoding="utf-8") as csv_file:
             writer = csv.DictWriter(csv_file, fieldnames=fieldnames)