title: Argument of type 'FormGroup' is not assignable to parameter of type 'string'
body: <p>I have the following function that shows the following error in the  - Can anyone suggest why I am getting this error?</p>
  
  <pre><code>export class QuestionComponent implements OnInit {
  
    questionnaire: FormGroup;
    items;
    constructor(private formBuilder: FormBuilder, private postDataIntoDB: ServerService) { }
  
    ngOnInit() {
    this.questionnaire = this.formBuilder.group({
    items: this.formBuilder.array([this.createItem()])
  });}
  
    createItem(): FormGroup {
        return this.formBuilder.group({
        sno: ['',Validators.required],
        question:['',Validators.required],
        option1: ['',Validators.required],
        option2: ['',Validators.required],
        option3: ['',Validators.required],
        option4: ['',Validators.required],
        option5: ['',Validators.required]
  });}
  
    addItem(): void {
       this.items = this.questionnaire.get('items') as FormArray;
       this.items.push(this.createItem());
  }}
  </code></pre>
  
  <p>I am getting error on <code>this.postDataIntoDB.storeData(this.questionnaire)</code>:</p>
  
  <blockquote>
    <p>Argument of type'FormGroup' is not assignable to parameter of type
    'string'</p>
  </blockquote>
  
  <pre><code>onSubmit() {
      this.postDataIntoDB.storeData(this.questionnaire)
        .subscribe(
          (response) =&gt; console.log(response),
            (error)=&gt; console.log(error)
       )}
  </code></pre>