def can_be_disabled(self, identifier):
        return self._dependency_graph.in_degree(identifier) == 0
Construct a CHECK constraint.
dataset/ETHPy150Open VisTrails/VisTrails/vistrails/core/packagemanager.py/PackageManager.can_be_disabled--crossover with--dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/sql/schema.py/CheckConstraint.__init__