added override for configured backupdir

adb.py

@@ -229,10 +229,13 @@ class Device:
                 self.shell("input","text",str(password))
                 self.send_keycode('enter')
 
-    def backup(self,*partitions,name = None):
+    def backup(self,*partitions,name = None,backupdir = None):
         if self.mode != 'recovery':
             self.reboot('recovery')
-        backupdir = config['local']['twrp']
+        if backupdir is None:
+            backupdir = config['local']['twrp']
+        else:
+            backupdir = backupdir
         options_dict = {
             "system": "S",
             "data": "D",