code: public Observable<List<PartitionMetricInner>> listMetricsAsync(String resourceGroupName, String accountName, String databaseRid, String collectionRid, String filter) {
          return listMetricsWithServiceResponseAsync(resourceGroupName, accountName, databaseRid, collectionRid, filter).map(new Func1<ServiceResponse<List<PartitionMetricInner>>, List<PartitionMetricInner>>() {
              @Override
              public List<PartitionMetricInner> call(ServiceResponse<List<PartitionMetricInner>> response) {
                  return response.body();
              }
          });
      }
docs: Retrieves the metrics determined by the given filter for the given collection, split by partition.
  
  @param resourceGroupName Name of an Azure resource group.
  @param accountName Cosmos DB database account name.
  @param databaseRid Cosmos DB database rid.
  @param collectionRid Cosmos DB collection rid.
  @param filter An OData filter expression that describes a subset of metrics to return. The parameters that can be filtered are name.value (name of the metric, can have an or of multiple names), startTime, endTime, and timeGrain. The supported operator is eq.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the List&lt;PartitionMetricInner&gt; object