title: Cannot import Observable.fromEvent - RXJS
body: <p>I'm trying to create an Observable from an input event. I have already tried almost everything and I can not import "fromEvent". This is my code. I am using angular 6.0.1 and RXJS 6.1.0</p>
  
  <p><strong>error TS2339: Property 'fromEvent' does not exist on type 'typeof Observable'.</strong></p>
  
  <pre><code>import { Directive, EventEmitter, Input, Output, ElementRef, ViewChild, AfterViewInit } from '@angular/core';
  import { NgControl } from '@angular/forms';
  import { distinctUntilChanged } from 'rxjs/internal/operators/distinctUntilChanged';
  import { debounceTime } from 'rxjs/internal/operators/debounceTime';
  import { map } from 'rxjs/internal/operators/map';
  import { filter } from 'rxjs/internal/operators/filter';
  import { Observable } from 'rxjs/internal/Observable';
  //import 'rxjs/internal/observable/fromEvent';
  //import 'rxjs/add/observable/fromEvent';
  
  @Directive({
    selector: '[ngModel][debounceTime]'
  })
  export class InputDebounceDirective implements AfterViewInit {
  
    @Output()
    public onDebounce = new EventEmitter&lt;any&gt;();
  
    @Input('debounceTime')
    public debounceTime: number = 1500;
  
    constructor(private elementRef: ElementRef, private currentModel: NgControl) { }
  
    ngAfterViewInit() {
      Observable.fromEvent(this.elementRef.nativeElement, 'keyup')
        .pipe(
          debounceTime(this.debounceTime),
          distinctUntilChanged()
        )
        .subscribe(x =&gt; {
          this.onDebounce.emit(x);
        });
  
    }
  
  }
  </code></pre>