New in version 2.6.
True when expr is a sequence of Abjad notes:
abjad> notes = [Note("c'4"), Note("d'4"), Note("e'4")]
abjad> notetools.all_are_notes(notes)
True
True when expr is an empty sequence:
abjad> notetools.all_are_notes([])
True
Otherwise false:
abjad> notetools.all_are_notes('foo')
False
Return boolean.
Function wraps componenttools.all_are_components().