Codepipeline using cdk with source as S3 and deploy as AppConfig

I have started my cdk, somedays ago and having this problem from 1-2 days. If someone could give insights it would be very helpful
Following is the code for the pipeline and receiving error:
throw new Error(‘Trying to resolve() a Construct at ‘ + pathName);

export class AppConfigCiCdStack extends Stack {
    private application: CfnApplication;
    private environments: CfnEnvironment;
    private deploymentStrategy: CfnDeploymentStrategy;
    private bucket: Bucket;
    private profile: CfnConfigurationProfile
    constructor(scope: Construct, id: string, props?: StackProps) {
        super(scope, id, props);

        this.application = new CfnApplication(this, "ServerlessApplication", {
            description: "ConFiguration For Serverless Application",
            name: "ServerlessApplicationConfig"
        });

        this.environments = new CfnEnvironment(this, "Testing", {
            description: "Testing environment for app",
            name : "Test",
            applicationId : this.application.ref,
        });

        this.profile = new CfnConfigurationProfile(this, "LoggingConfiguration", {
            applicationId: this.application.ref,
            description : "Logging related configuration",
            name: "LoggingConfiguration",
            locationUri: `s3://${this.bucket}sampleApp.zip/`
        })
        
        this.bucket = new Bucket(this, 'source', {
            bucketName: 'source',
            versioned: true,
        })

        this.deploymentStrategy = new CfnDeploymentStrategy(this, "DeploymentStrategy", {
            deploymentDurationInMinutes : 0,
            finalBakeTimeInMinutes: 1,
            growthType: "LINEAR",
            growthFactor: 100,
            name: "Custom.Immediate.Bake5Minutes",
            replicateTo: "NONE",
        })

        this.pipeline(this.bucket, this.application, this.environments, this.deploymentStrategy, this.profile);
    }

    pipeline(bucket: Bucket, application: CfnApplication, environments: CfnEnvironment, strategy: CfnDeploymentStrategy, profile: CfnConfigurationProfile) {
        
        const pipelineArtifact = new Bucket(this, "serverlessappconfigpipelineartifact", {
            bucketName: "serverlessappconfigpipelineartifact",
            versioned: true,
            autoDeleteObjects: true, 
            removalPolicy: RemovalPolicy.DESTROY,
        })

        const sourceConfig = {"Application": application.ref, "Bucket": bucket, "S3ObjectKey": 'sampleApp.zip'};

        const outputArtifactProperty: CfnPipeline.OutputArtifactProperty = {
            name: 'sourceConfig',
        };

        const inputArtifactProperty: CfnPipeline.InputArtifactProperty = {
            name: 'sourceConfig',
        };

        const configSource : CfnPipeline.ActionDeclarationProperty = {
            actionTypeId: {
                category: "Source", 
                owner: "AWS",
                provider: "S3",
                version: "1",
            },
            configuration: {
                sourceConfig,
            },
            name: "ServerlessAppConfigSource",
            outputArtifacts: [outputArtifactProperty],
        }

        const sourceStage: CfnPipeline.StageDeclarationProperty = {
            name: "Source",
            actions: [configSource],
        }

        const deployConfig = {  "Application": application.ref, 
                                "Environment": environments.ref, 
                                "ConfigurationProfile": profile.ref, 
                                "DeploymentStrategy": strategy.ref,
                                "InputArtifactConfigurationPath": 'sampleApp.json'};

        const appConfigDeploy: CfnPipeline.ActionDeclarationProperty = {
            actionTypeId: {
                category: "Deploy",
                owner: "AWS",
                provider: "AppConfig",
                version: '1',
            },
            inputArtifacts: [inputArtifactProperty],
            configuration: deployConfig,
            name: "ServerlessAppConfigDeploy",
        }

        const deployStage : CfnPipeline.StageDeclarationProperty = {
            name: "Deploy",
            actions: [appConfigDeploy],
        }

        const artifactStoreProperty: CfnPipeline.ArtifactStoreProperty = {
            location: pipelineArtifact.bucketName,
            type: "S3",
        }

        const pipeline = new CfnPipeline(this, "ServerlessAppConfigPipeline", {
            stages: [sourceStage, deployStage],
            artifactStore: artifactStoreProperty,
            roleArn: '',
            name: 'ServerlessAppConfigPipeline'
        })
    }

}

error: throw new Error(‘Trying to resolve() a Construct at ‘ + pathName);