New in version 2.0.
True when expr is a LilyPond duartion name:
abjad> from abjad.tools import durationtools
abjad> durationtools.is_lilypond_duration_name('\\breve')
True
Otherwise false:
abjad> durationtools.is_lilypond_duration_name('foo')
False
The regex ^(\\breve|\\longa|\\maxima)$ underlies this predicate.
Return boolean.