You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: data_tree_navigator.go
    path of file: ./repos/yq/pkg/yqlib
    
    the code of the file until where you have to start completion: package yqlib

import (
	"fmt"

	logging "gopkg.in/op/go-logging.v1"
)

type DataTreeNavigator interface {
	// given the context and an expressionNode,
	// this will process the against the given expressionNode and return
	// a new context of matching candidates
	GetMatchingNodes(context Context, expressionNode *ExpressionNode) (Context, error)

	DeeplyAssign(context Context, path []interface{}, rhsNode *CandidateNode) error
}

type dataTreeNavigator struct {
}

func NewDataTreeNavigator() DataTreeNavigator {
	return &dataTreeNavigator{}
}

func (d *dataTreeNavigator) Deepl
    
func (d *dataTreeNavigator) GetMatchingNodes(context Context, expressionNode *ExpressionNode) (Context, error) {
	if expressionNode == nil {
		log.Debugf("getMatchingNodes - nothing to do")
		return context, nil
	}
	log.Debugf("Processing Op: %v", expressionNode.Operation.toString())
	if log.IsEnabledFor(logging.DEBUG) {
		for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
			log.Debug(NodeToString(el.Value.(*CandidateNode)))
		}
	}
	handler := expressionNode.Operation.OperationType.Handler
	if handler != nil {
		return handler(d, context, expressionNode)
	}
	return Context{}, fmt.Errorf("Unknown operator %v", expressionNode.Operation.OperationType)

}