Godeps/_workspace/src/gopkg.in/mgo.v2/session.go
func (c *Collection) Remove(selector interface{}) error {
	lerr, err := c.writeQuery(&deleteOp{c.FullName, selector, 1})
	if err == nil && lerr != nil && lerr.N == 0 {
		return ErrNotFound
	}
	return err
}
func (c *Collection) Remove(selector interface{}) error {
	lerr, err := c.writeQuery(&deleteOp{c.FullName, selector, 1})
	if err == nil && lerr != nil && lerr.N == 0 {
		return ErrNotFound
	}
	return err
}
// Remove finds a single document matching the provided selector document
// and removes it from the database.
// If the session is in safe mode (see SetSafe) a ErrNotFound error is
// returned if a document isn't found, or a value of type *LastError
// when some other error is detected.
//
// Relevant documentation:
//
//     http://www.mongodb.org/display/DOCS/Removing
//