[BUG] - problem in calling api functions

Hi @KensingtonTech 
thank for this awesome package. that's really nice.
I have a problem in calling api functions.
when I  try to call each functions, in browser console this error appeared:
   Error: this.panZoomAPI.[function name] is not a function


[https://stackblitz.com/edit/ngx-panzoom-test-10-2-lkqk3x?file=src%2Fapp%2Fapp.component.ts]

