Expected case for triads?

[CookieComputing]

I'm not sure what the expected case is for a lowercase note:

>>> chords.triads("C")
[['C', 'E', 'G'], ['D', 'F', 'A'], ['E', 'G', 'B'], ['F', 'A', 'C'], ['G', 'B', 'D'], ['A', 'C', 'E'], ['B', 'D', 'F']]
>>> chords.triads("c")
[['C', 'Eb', 'G'], ['D', 'F', 'Ab'], ['Eb', 'G', 'Bb'], ['F', 'Ab', 'C'], ['G', 'Bb', 'D'], ['Ab', 'C', 'Eb'], ['Bb', 'D', 'F']]

The triads returned for "C" are correct, but it seems like "c" returns different triads.

I'm not particularly versed enough in theory to figure out if this is correct behavior.