CocoaLumberjack Custom Crashlytics Logger in Swift

CrashlyticsLogger.swift

import Foundation
import CocoaLumberjack
import Crashlytics

class CrashlyticsLogger : DDAbstractLogger
{
    static let sharedInstance = CrashlyticsLogger()
    
    private var _logFormatter : DDLogFormatter?
    override var logFormatter: DDLogFormatter? {
        get {
            return _logFormatter
        }
        set {
            _logFormatter = newValue
        }
    }
    
    override func logMessage(logMessage: DDLogMessage)
    {
        guard let formatter = self.logFormatter
        else
        {
            print("CrashlyticsLogger: No formatter")
            return
        }
        
        let formattedMessage = formatter.formatLogMessage(logMessage)
        CLSLogv(formattedMessage, getVaList([]))
    }
}

Tried to implement this but am wondering where CustomLogFormatter() is defined?