Sorry, I missed something in description. Nice kata!

Please, test this:

assert.strictEqual(HarmoniousArray([ [ 219, 165, 229, 164, 207, 182, 186, 134, 188 ],
  [ 215, 208, 161, 222, 191, 135, 175, 155, 131 ],
  [ 146, 205, 229, 203, 223, 153, 139, 221, 212 ],
  [ 140, 158, 184, 210, 134, 160, 182, 214, 153 ],
  [ 172, 145, 226, 170, 156, 197, 146, 204, 208 ] ], 35), 5)
});
  
It should be 6 heads.

[[205, 229, 203],
[158, 184, 210]]

Thanks.

JS version
Are you sure about random tests? Most of them expect Expected: 2496.
I can only pass fixed tests :(

Sorry for my bad python code (translated from js).
Approved!

Your randomString() function which is "not defined" is inside refSol() function. Move randomString() function before any tests. Then you can use your solution for refSol() function.

Very nice!

This is duplicate!

It is easy to overlook:

...
if len(stack) == 0:
    return True
return False 

.

I assessed this kata as 6kyu. Average assessment at that moment was 4kyu, but now is more realistic :).

This kata needs random tests.