@classmethod
    def coerce(cls, key, value):
        if not isinstance(value, MutableDict):
            if isinstance(value, dict):
                return MutableDict(value)

            # this call will raise ValueError
            return mutable.Mutable.coerce(key, value)
        else:
            return value
Convert plain dictionaries to MutableDict.
dataset/ETHPy150Open openstack/sahara/sahara/db/sqlalchemy/types.py/MutableDict.coerce