# Extending OpenAPI

There are some cases where you might need to modify the generated OpenAPI schema.

In this section you will see how.

## The normal process

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

		switch {
		case isSysErrNotDir(err) && !osIsNotExist(err):
			// Windows can have both isSysErrNotDir(err) and osIsNotExist(err) returning
			// true if the source file path contains an non-existent directory. In that case,
			// we want to return errFileNotFound instead, which will honored in subsequent
			// switch cases
			return errFileAccessDenied
		case isSysErrPathNotFound(err):

This also means that in many cases you can pass the same object you get from a request **directly to the database**, as everything is validated automatically.

The same applies the other way around, in many cases you can just pass the object you get from the database **directly to the client**.

scope: WORKLOAD_SELECTOR
```

The above policies reject unauthenticated traffic at the ztunnel unless its destination is port 9090. For more complete examples, read through the [test cases](../../pilot/pkg/serviceregistry/kube/controller/ambientindex_test.go) in the `TestRBACConvert` function.

## PeerAuthentication and the Waypoint Proxy

			nil,
			nil,
		},
		// Test - 4 - parse the chunk reader properly.
		{
			bufio.NewReader(readers[3]),
			nil,
			[]byte("1000"),
			[]byte("111123333333333333334444211"),
		},
	}
	// Valid test cases for each chunk line.
	for i, tt := range testCases {
		chunkSize, chunkSignature, err := readChunkLine(tt.reader)
		if err != tt.expectedErr {
			t.Errorf("Test %d: Expected %s, got %s", i+1, tt.expectedErr, err)
		}

  }

  /*
   * AbstractCollection fails the removeAll(null) test when the subject
   * collection is empty, but we'd still like to test removeAll(null) when we
   * can. We split the test into empty and non-empty cases. This allows us to
   * suppress only the former.
   */

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(ZERO)
  public void testRemoveAll_nullCollectionReferenceEmptySubject() {

			}

			if opts.Interface != "" {
				if h, _, err := net.SplitHostPort(address); err == nil {
					address = h
				}
				// Create socket on specific vrf device.
				// To catch all kinds of special cases this filters specifically for loopback networks.
				if ip := net.ParseIP(address); ip != nil && !ip.IsLoopback() {
					_ = syscall.SetsockoptString(fd, syscall.SOL_SOCKET, syscall.SO_BINDTODEVICE, opts.Interface)
				}
			}

    * So, by using FastAPI you are saving development time, bugs, lines of code, and you would probably get the same performance (or better) you would...

				}
				c.Audience, err = jsonparser.ParseString(value)
				return err
			}
		case 'e':
			if string(key) == "exp" {
				if dataType != jsonparser.Number {
					return errors.New("exp: Expected number")
				}
				c.ExpiresAt, err = jsonparser.ParseInt(value)
				return err
			}
		case 'i':
			if string(key) == "iat" {
				if dataType != jsonparser.Number {

---

**Note**: You can mix `def` and `async def` in your *path operation functions* as much as you need and define each one using the best option for you. FastAPI will do the right thing with them.

Anyway, in any of the cases above, FastAPI will still work asynchronously and be extremely fast.

But by following the steps above, it will be able to do some performance optimizations.

## Technical Details