context.go
func (c *Context) Query() bson.M {
	return bson.M{"$and": append([]bson.M{c.Selector}, c.Filters...)}
}
func (c *Context) Query() bson.M {
	return bson.M{"$and": append([]bson.M{c.Selector}, c.Filters...)}
}
// Query returns the composite query of Selector and Filter.