code: public Observable<Page<ManagedInstanceKeyInner>> listByInstanceAsync(final String resourceGroupName, final String managedInstanceName, final String filter) {
          return listByInstanceWithServiceResponseAsync(resourceGroupName, managedInstanceName, filter)
              .map(new Func1<ServiceResponse<Page<ManagedInstanceKeyInner>>, Page<ManagedInstanceKeyInner>>() {
                  @Override
                  public Page<ManagedInstanceKeyInner> call(ServiceResponse<Page<ManagedInstanceKeyInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Gets a list of managed instance keys.
  
  @param resourceGroupName The name of the resource group that contains the resource. You can obtain this value from the Azure Resource Manager API or the portal.
  @param managedInstanceName The name of the managed instance.
  @param filter An OData filter expression that filters elements in the collection.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;ManagedInstanceKeyInner&gt; object