New in version 2.6.
True when expr is a sequence of Abjad rests:
abjad> rests = [Rest('r4'), Rest('r4'), Rest('r4')]
abjad> resttools.all_are_rests(rests)
True
True when expr is an empty sequence:
abjad> resttools.all_are_rests([])
True
Otherwise false:
abjad> resttools.all_are_rests('foo')
False
Return boolean.
Function wraps componenttools.all_are_components().