{* ../../docs_src/query_params/tutorial004_py310.py hl[6,8] *}

## Required query parameters { #required-query-parameters }

When you declare a default value for non-path parameters (for now, we have only seen query parameters), then it is not required.

If you don't want to add a specific value but just make it optional, set the default as `None`.

We can do better...

## What makes a dependency { #what-makes-a-dependency }

Up to now you have seen dependencies declared as functions.

But that's not the only way to declare dependencies (although it would probably be the more common).

The key factor is that a dependency should be a "callable".

{* ../../docs_src/path_operation_advanced_configuration/tutorial004.py hl[19:29] *}

## Additional Responses { #additional-responses }

You probably have seen how to declare the `response_model` and `status_code` for a *path operation*.

That defines the metadata about the main response of a *path operation*.

  // the "short hash".
  //
  // The `keys`, `values`, and `entries` arrays always have the same size as each other. They can be
  // seen as fields of an imaginary `Entry` object like this:
  //
  // class Entry {
  //    int hash;
  //    Entry next;
  //    K key;
  //    V value;
  // }
  //

        if ((createOptions & 0x0001) == 0) {
            this.createOptions = createOptions | 0x0040;
        } else {
            this.createOptions = createOptions;
        }
        this.impersonationLevel = 0x02; // As seen on NT :~)
        this.securityFlags = (byte) 0x03; // SECURITY_CONTEXT_TRACKING | SECURITY_EFFECTIVE_ONLY
    }

    /**
     * {@inheritDoc}
     *

        // Reserved (4 bytes) - The implementation skips writing these bytes,
        // so they will have the initial pattern (0xCCCCCCCC)
        // This is expected behavior as seen in the implementation at line 131
        assertEquals((byte) 0xCC, buffer[4]);
        assertEquals((byte) 0xCC, buffer[5]);
        assertEquals((byte) 0xCC, buffer[6]);
        assertEquals((byte) 0xCC, buffer[7]);

| `minio_replication_max_active_workers`            | Maximum number of active replication workers seen since server start. <br><br>Type: gauge   | `server` |
| `minio_replication_max_queued_bytes`              | Maximum number of bytes queued for replication since server start. <br><br>Type: gauge      | `server` |

You can learn how to use them and how they are integrated into **FastAPI** later in the **Advanced User Guide**.

## Recap { #recap }

With what you have seen up to now, you can set up a secure **FastAPI** application using standards like OAuth2 and JWT.

In almost any framework handling the security becomes a rather complex subject quite quickly.

  // the "short hash".
  //
  // The `keys`, `values`, and `entries` arrays always have the same size as each other. They can be
  // seen as fields of an imaginary `Entry` object like this:
  //
  // class Entry {
  //    int hash;
  //    Entry next;
  //    K key;
  //    V value;
  // }
  //

	return MetricDescription{
		Namespace: nodeMetricNamespace,
		Subsystem: replicationSubsystem,
		Name:      recentBacklogCount,
		Help:      "Total number of objects seen in replication backlog in the last 5 minutes",
		Type:      gaugeMetric,
	}
}

func getClusterRepCredentialErrorsMD(namespace MetricNamespace) MetricDescription {
	return MetricDescription{