# Support

Here are some resources to help you understand and use Istio:

- For in-depth information about how to use Istio, visit [istio.io](https://istio.io)
- To ask questions and get assistance from our community, visit [GitHub Discussions](https://github.com/istio/istio/discussions)

## Check the Docs

You can see the query parameters in the docs UI at `/docs`:

<div class="screenshot">
<img src="/img/tutorial/query-param-models/image01.png">
</div>

## Forbid Extra Query Parameters

In some special use cases (probably not very common), you might want to **restrict** the query parameters that you want to receive.

You can use Pydantic's model configuration to `forbid` any `extra` fields:

//// tab | Python 3.10+

	// If x-amz-content-sha256 is set and the value is not
	// 'UNSIGNED-PAYLOAD' we should validate the content sha256.
	switch v[0] {
	case unsignedPayload, unsignedPayloadTrailer:
		return true
	case emptySHA256:
		// some broken clients set empty-sha256
		// with > 0 content-length in the body,
		// we should skip such clients and allow
		// blindly such insecure clients only if
		// S3 strict compatibility is disabled.

// Package-wide variables from generator "generated".
option go_package = "k8s.io/api/events/v1";

// Event is a report of an event somewhere in the cluster. It generally denotes some state change in the system.
// Events have a limited retention time and triggers and messages may evolve
// with time.  Event consumers should not rely on the timing of an event

@app.get("/items/{item_id}")
async def read_item(item_id: str):
    if item_id not in items:
        raise HTTPException(
            status_code=404,
            detail="Item not found",
            headers={"X-Error": "Some custom header"},
        )
    return {"item": items[item_id]}


@app.get("/http-no-body-statuscode-exception")
async def no_body_status_code_exception():
    raise HTTPException(status_code=204)

/**
 * Collects, flattens and resolves dependencies.
 */
@Experimental
public interface DependencyResolver extends Service {

    /**
     * Collects the transitive dependencies of some artifacts and builds a dependency graph for the given path scope.
     * Note that this operation is only concerned about determining the coordinates of the transitive dependencies and
     * does not actually resolve the artifact files.

     * is given by {@link #getSource()}.
     *
     * @return The one-based index of the line containing the problem or a non-positive value if unknown.
     */
    int getLineNumber();

    /**
     * Gets the one-based index of the column containing the problem. The column number should refer to some text file
     * that is given by {@link #getSource()}.
     *

					toSend = append(toSend, payload...)
					select {
					case <-ctx.Done():
						return nil
					case out <- toSend:
					}
				}
				return nil
			},

			Subroute:    "some-subroute",
			OutCapacity: 1, // Only one message buffered.
			InCapacity:  0,
		}))
		errFatal(err)
	}
	const payloadSize = 512
	rng := rand.New(rand.NewSource(time.Now().UnixNano()))

```

////

/// warning

Before setting `convert_underscores` to `False`, bear in mind that some HTTP proxies and servers disallow the usage of headers with underscores.

///

## Duplicate headers

It is possible to receive duplicate headers. That means, the same header with multiple values.

You can define those cases using a list in the type declaration.

    if model_name.value == "lenet":
        return {"model_name": model_name, "message": "LeCNN all the images"}