TypeError: unhashable type: 'list'

[ronald.kevin.burton at gmail.com]

I am getting an exception that the traceback looks like:

------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Projects\QA\robot_20141103\resources\assessment_utilities.py", line 29, in create_new_project
    program = customer.add(program_code)
  File "C:\Projects\QA\robot_20141103\resources\assessment_customer.py", line 589, in add
    program = ProgramMaker.Code2Program(program_code, self)
  File "C:\Projects\QA\robot_20141103\resources\programmaker.py", line 25, in Code2Program
    'ASSESS_PPL' : PPL(customer)
  File "C:\Projects\QA\robot_20141103\resources\ppl.py", line 20, in __init__
    MeasureMaker.Code2Measure('Furnace Whistle', self)
TypeError: unhashable type: 'list'
------------------------------------------------------------	

My problem is that I am not sure what the problem is. I can check the type of 'self' which is an object and the string 'Furnace Whistle' is obviously not a list. The static function 'MeasureMaker.Code2Measure' is a simple factory:

class MeasureMaker:

    def Code2Measure(measure_code, core):
        try:
            return {
...
                'Furnace Whistle': FurnaceWhistle(core)
            }[measure_code]
        except KeyError as error:
            return None
    Code2Measure = staticmethod(Code2Measure)

What is the 'list' that is in the exception? Or how do I find out?

Thank you.

Kevin