CNN - Попытка запустить беспорядочную матрицу, используя seaborn.heatmap

//in the ts file
 constructor( public db: AngularFireDatabase) {
  this.items = db.list('items').valueChanges();
  db.list('/sentences').valueChanges().subscribe(sentences => {
    this.sentences = sentences;
    console.log(this.sentences);
    this.labels = this.sentences; //in this.labels we have all the elements *declaration : labels=[]
    console.log(this.labels);

  }); 
onSkip($i) {
  if (this.i > 13) { //if there are 13 elements in the database
    this.i = 0;
  }

  this.i = this.i + 1;
  console.log(this.i);
}    

 // in the html code
 {{labels[i]}}  

 <button class="centered" (click)="onSkip(i)" > SKIP  <a routerLink="skip">