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: formatter.go
    path of file: ./repos/kubernetes/vendor/github.com/sirupsen/logrus
    
    the code of the file until where you have to start completion: package logrus

import "time"

// Default key names for the default fields
const (
	defaultTimestampFormat = time.RFC3339
	FieldKeyMsg            = "msg"
	FieldKeyLevel          = "level"
	FieldKeyTime           = "time"
	FieldKeyLogrusError    = "logrus_error"
	FieldKeyFunc           = "func"
	FieldKeyFile           = "file"
)

// The Formatter interface is used to implement a custom Formatter. It takes an
// `Entry`. It exposes all the fields, including the default ones:
//
// * `entry.Data["msg"]`. The message passed from Info, Warn, Error ..
// * `entry.Data["time"]`. The timestamp.
// * `entry.Data["level"]. The level the entry was logged at.
//
// Any additional fields added with `WithField` or `WithFields` are also in
// `entry.Data`. Format is
    
func prefixFieldClashes(data Fields, fieldMap FieldMap, reportCaller bool) {
	timeKey := fieldMap.resolve(FieldKeyTime)
	if t, ok := data[timeKey]; ok {
		data["fields."+timeKey] = t
		delete(data, timeKey)
	}

	msgKey := fieldMap.resolve(FieldKeyMsg)
	if m, ok := data[msgKey]; ok {
		data["fields."+msgKey] = m
		delete(data, msgKey)
	}

	levelKey := fieldMap.resolve(FieldKeyLevel)
	if l, ok := data[levelKey]; ok {
		data["fields."+levelKey] = l
		delete(data, levelKey)
	}

	logrusErrKey := fieldMap.resolve(FieldKeyLogrusError)
	if l, ok := data[logrusErrKey]; ok {
		data["fields."+logrusErrKey] = l
		delete(data, logrusErrKey)
	}

	// If reportCaller is not set, 'func' will not conflict.
	if reportCaller {
		funcKey := fieldMap.resolve(FieldKeyFunc)
		if l, ok := data[funcKey]; ok {
			data["fields."+funcKey] = l
		}
		fileKey := fieldMap.resolve(FieldKeyFile)
		if l, ok := data[fileKey]; ok {
			data["fields."+fileKey] = l
		}
	}
}