Run every check in the check module against expr.
Set the runtime keyword to composition to run only those checks appropriate at composition-time. Abjad allows empty containers at composition-time. Empty container checks will NOT run.
abjad> check.wf(Voice([ ]), runtime = 'composition')
True
Set the runtime keyword to format to run the complete set of checks appropriate at format-time. LilyPond does NOT allow empty containers at format-time. Empty container check WILL run.
abjad> check.wf(Voice([ ]), runtime = 'format')
False