code: public Observable<Page<RoleAssignmentInner>> listByResourceGroupAsync(final String resourceGroupName, final String filter) {
          return listByResourceGroupWithServiceResponseAsync(resourceGroupName, filter)
              .map(new Func1<ServiceResponse<Page<RoleAssignmentInner>>, Page<RoleAssignmentInner>>() {
                  @Override
                  public Page<RoleAssignmentInner> call(ServiceResponse<Page<RoleAssignmentInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Gets role assignments for a resource group.
  
  @param resourceGroupName The name of the resource group.
  @param filter The filter to apply on the operation. Use $filter=atScope() to return all role assignments at or above the scope. Use $filter=principalId eq {id} to return all role assignments at, above or below the scope for the specified principal.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;RoleAssignmentInner&gt; object