func (tree *ExpressionTree) GetBSON() (interface{}, error) {
	if tree == nil || tree.Expression == nil {
		return nil, nil
	}

	exprList, err := marshalAssumesExpressionTree(tree)
	if err != nil {
		return nil, errors.Trace(err)
	}
	return exprList, nil
}
// GetBSON implements the bson.Getter interface.
GetBSON implements the bson.Getter interface.
// GetBSON implements the bson . Getter interface .
func (tree *ExpressionTree) GetBSON() (interface{}, error) {
	if tree == nil || tree.Expression == nil {
		return nil, nil
	}
	exprList, err := marshalAssumesExpressionTree(tree)
	if err != nil {
		return nil, errors.Trace(err)
	}
	return exprList, nil
}
func ( tree * ExpressionTree ) GetBSON ( ) ( interface { } , error ) { if tree == nil || tree . Expression == nil { return nil , nil } exprList , err := marshalAssumesExpressionTree ( tree ) if err != nil { return nil , errors . Trace ( err ) } return exprList , nil }
GetBSON implements the bson.Getter interface.
GetBSON implements the bson . Getter interface .