castIn (value) {
        var handler = Variable.types[this.type] || Variable.types.any;

        return _.isFunction(handler) ? handler(value) : handler.in(value);
    }
Typecasts a value to the {@link Variable.types} of this {@link Variable}. Returns the value of the variable
converted to the type specified in {@link Variable#type}.

@private
@param {*} value -
@returns {*}