'Run hooked-in checks'

def check_hook(self):

    cond = True
    check = self.check
    if (check is not None):
        if (not isinstance(check, (list, tuple))):
            check = [check]
        for condition in check:
            if (callable(condition) and (not condition(self))):
                cond = False
            elif (not condition):
                cond = False
    return cond
