New in version 2.0.
True when expr is a sequence and all elements in expr are nonnegative integers:
abjad> from abjad.tools import sequencetools
abjad> sequencetools.all_are_nonnegative_integers([0, 1, 2, 99])
True
Otherwise false:
abjad> sequencetools.all_are_nonnegative_integers([0, 1, 2, -99])
False
Return boolean.