New in version 2.0.
Analyze tonal function of expr according to key_signature:
abjad> from abjad.tools import tonalitytools
abjad> chord = Chord("<c' e'>4")
abjad> key_signature = contexttools.KeySignatureMark('g', 'major')
abjad> tonalitytools.analyze_incomplete_tonal_function(chord, key_signature)
IVMajorTriadInRootPosition
Return tonal function.