Mask doesn't work on latest Xcode and swift

error as follows:

(lldb) mask self.testView
error: error: use of undeclared identifier 'self'
error: error: use of undeclared identifier 'None'
error: error: use of undeclared identifier 'None'
error: error: use of undeclared identifier 'None'
Traceback (most recent call last):
File "/usr/local/opt/chisel/libexec/fblldb.py", line 83, in runCommand
command.run(args, options)
File "/usr/local/Cellar/chisel/1.5.0/libexec/commands/FBDisplayCommands.py", line 153, in run
viewHelpers.maskView(viewOrLayer, options.color, options.alpha)
File "/usr/local/opt/chisel/libexec/fblldbviewhelpers.py", line 25, in maskView
origin = convertPoint(0, 0, viewOrLayer, window)
File "/usr/local/opt/chisel/libexec/fblldbviewhelpers.py", line 47, in convertPoint
fromLayer = convertToLayer(fromViewOrLayer)
File "/usr/local/opt/chisel/libexec/fblldbviewhelpers.py", line 52, in convertToLayer
if fb.evaluateBooleanExpression('[(id)%s isKindOfClass:(Class)[CALayer class]]' % viewOrLayer):
File "/usr/local/opt/chisel/libexec/fblldbbase.py", line 84, in evaluateBooleanExpression
return (int(evaluateIntegerExpression('(BOOL)(' + expression + ')', printErrors)) != 0)
File "/usr/local/opt/chisel/libexec/fblldbbase.py", line 76, in evaluateIntegerExpression
output = evaluateExpression('(int)(' + expression + ')', printErrors).replace('\'', '')
AttributeError: 'NoneType' object has no attribute 'replace'