def add_operator_storage(klass):
    """ Add a member to the class named '__op_storage__'.

    This member will be added as needed, and can be used to store
    instance specific data needed by the operators. The value of the
    storage will be a sortedmap.

    """
    members = klass.members()
    if '__op_storage__' not in members:
        m = Typed(sortedmap, ())
        m.set_name('__op_storage__')
        m.set_index(len(members))
        members['__op_storage__'] = m
dataset/ETHPy150Open ContinuumIO/ashiba/enaml/enaml/core/operators.py/add_operator_storage/original