Access to kerning pairs in the font

Hello, I’m trying to access the kerning object with the following code from the docu:

print(font.kerningForPair(, ‘A’, ‘V’))

I was expecting to get the kerning value for the pair, but I receive the following output:

I tried replacing the glyphs names by its kerning groups name
print(f.kerningForPair(, ‘@LAT_V_UC_1ST’, ‘@LAT_A_UC_2ND’))
but I obtain the same result.

I’m working directly on the Macro Panel
Any feedback would be appreciated. Thanks.

That number is NSNotFound, the system constant for ‘not available’. That means that pair has no kerning.