code: public Observable<Page<PolicyDefinitionInner>> listByManagementGroupNextAsync(final String nextPageLink) {
          return listByManagementGroupNextWithServiceResponseAsync(nextPageLink)
              .map(new Func1<ServiceResponse<Page<PolicyDefinitionInner>>, Page<PolicyDefinitionInner>>() {
                  @Override
                  public Page<PolicyDefinitionInner> call(ServiceResponse<Page<PolicyDefinitionInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Gets all the policy definitions for a subscription at management group level.
  
  @param nextPageLink The NextLink from the previous successful call to List operation.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;PolicyDefinitionInner&gt; object