title: Error: Property 'pipe' does not exist on type 'Observable<any>'
body: <p>I'm copy pasting one of the examples from here:</p>
  
  <p><a href="https://material.angular.io/components/autocomplete/overview" rel="noreferrer">https://material.angular.io/components/autocomplete/overview</a></p>
  
  <p><strong>HTML:</strong></p>
  
  <p></p>
  
  <pre><code>&lt;form class="example-form"&gt;
    &lt;mat-form-field class="example-full-width"&gt;
      &lt;input type="text" placeholder="Pick one" aria-label="Number" matInput [formControl]="myControl" [matAutocomplete]="auto"&gt;
      &lt;mat-autocomplete #auto="matAutocomplete"&gt;
        &lt;mat-option *ngFor="let option of filteredOptions | async" [value]="option"&gt;
          {{ option }}
        &lt;/mat-option&gt;
      &lt;/mat-autocomplete&gt;
    &lt;/mat-form-field&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p><strong>TS:</strong></p>
  
  <pre><code>import {Component} from '@angular/core';
  import {FormControl} from '@angular/forms';
  import {Observable} from 'rxjs/Observable';
  import {startWith} from 'rxjs/operators/startWith';
  import {map} from 'rxjs/operators/map';
  
  /**
   * @title Filter autocomplete
   */
  @Component({
    selector: 'autocomplete-filter-example',
    templateUrl: 'autocomplete-filter-example.html',
    styleUrls: ['autocomplete-filter-example.css']
  })
  export class AutocompleteFilterExample {
  
    myControl: FormControl = new FormControl();
  
    options = [
      'One',
      'Two',
      'Three'
    ];
  
    filteredOptions: Observable&lt;string[]&gt;;
  
    ngOnInit() {
      this.filteredOptions = this.myControl.valueChanges
        .pipe(
          startWith(''),
          map(val =&gt; this.filter(val))
        );
    }
  
    filter(val: string): string[] {
      return this.options.filter(option =&gt;
        option.toLowerCase().indexOf(val.toLowerCase()) === 0);
    }
  
  }
  </code></pre>
  
  <p><strong>CSS:</strong></p>
  
  <p></p>
  
  <pre><code>.example-form {
    min-width: 150px;
    max-width: 500px;
    width: 100%;
  }
  
  .example-full-width {
    width: 100%;
  }
  </code></pre>
  
  <p>But I get this error:</p>
  
  <blockquote>
    <p>Failed to compile: Property 'pipe' does not exist on type 'Observable'.</p>
  </blockquote>
  
  <p>Any idea why?</p>