New in version 2.6.
True when expr is a sequence of Abjad scores:
abjad> score = Score([Staff([Note("c'4")])])
abjad> score
Score<<1>>
abjad> scoretools.all_are_scores([score])
True
True when expr is an empty sequence:
abjad> scoretools.all_are_scores([])
True
Otherwise false:
abjad> scoretools.all_are_scores('foo')
False
Return boolean.
Function wraps componenttools.all_are_components().