ID 366901 - envelope.keyframes.setSlopeType() function fails with TypeError

Problem summary
envelope.keyframes.setSlopeType() function fails with TypeError. When running setSlopeType() Modo executes self._keyframe.SetSlope(stype), which then errors with TypeError: functiontakes exactly 2 arguments (1 given).

Customer reported version
modo.n/a

Customer reported platform
windows10

Steps to reproduce
1) Open Modo.
2) Select File>open and open the attached scene.
3) Select the scripting layout. Copy and paste the attached script into the script editor.
4) Right click the script editor and select "run"
Result: 

Traceback (most recent call last):
  File "<string>", line 11, in <module>
  File "F:\Modo121v2\extra\Python\modules\modo\channel.py", line 456, in setSlopeType
    self._keyframe.SetSlope(stype)
TypeError: function takes exactly 2 arguments (1 given)

Workaround
Unknown.

Reproduced by support
This bug has been reproduced in:
12.1v2 - Windows 10, OSX 10.13.5
12.0v1 - Windows 10
11.2v3 - Windows 10
11.2v1 - Windows 10
11.1v1 - Windows 10
11.0v3 - Windows 10
10.2v4 - Windows 10, OSX 10.13.5

Earliest version tested
10.2v4 - Windows 10, OSX 10.13.5 - This issue appears to be in all versions of the product
Expected behaviour
Included functions should not fail when the parent function is run.

Actual behaviour
The child function of keyframes.setSlopeType() calls for two arguments, however only one is specified. This results in a TypeError.