DB.Delete(&users3[0].Account)

	if err := DB.Preload(clause.Associations).Take(&user4, "id = ?", users3[0].ID).Error; err != nil || user4.Account.ID != 0 {
		t.Errorf("failed to query, got error %v, account: %#v", err, user4.Account)
	}

	if err := DB.Preload(clause.Associations, func(tx *gorm.DB) *gorm.DB {
		return tx.Unscoped()
	}).Take(&user4, "id = ?", users3[0].ID).Error; err != nil || user4.Account.ID == 0 {

      )
    server.useHttps(socketFactory)
    server.enqueue(
      MockResponse.Builder()
        .body("abc")
        .addHeader("Content-Type: text/plain")
        .build(),
    )

    // Make a request from client to server. It should succeed certificate checks (unfortunately the
    // rogue CA is trusted) but it should fail certificate pinning.
    val request =
      Request.Builder()

#
# The original version of this file is located in the https://github.com/istio/common-files repo.
# If you're looking at this file in a different repo and want to make a change, please go to the
# common-files repo, make the change there and check it in. Then come back to this repo and run
# "make update-common".

# Copyright Istio Authors
#
# Licensed under the Apache License, Version 2.0 (the "License");

    }

    taskFaker.runTasks()
    assertEvents(
      "take plan 0",
      "plan 0 TCP connecting...",
    )

    taskFaker.advanceUntil(250.ms)
    assertEvents(
      "take plan 1",
      "plan 1 TCP connecting...",
    )

    taskFaker.advanceUntil(500.ms)
    assertEvents(
      "take plan 2",
      "plan 0 cancel",
      "plan 1 cancel",
    )

  // Update the vector with information from `input_tensors` if provided.
  if (input_tensors != nullptr) {
    // Note that we take the address of the elements in `all_input_tensors`
    // below. Allocate enough space so that no reallocation happens, which will
    // make the pointers invalid.
    all_input_tensors.reserve(num_inputs);
    for (int i = 0; i < num_inputs; ++i) {

/// info

Keep in mind that the most important part to make a parameter optional is the part:

```Python
= None
```

or the:

```Python
= Query(default=None)
```

as it will use that `None` as the default value, and that way make the parameter **not required**.

## Install the Server Program

When you install FastAPI, it comes with a production server, Uvicorn, and you can start it with the `fastapi run` command.

But you can also install an ASGI server manually.

Make sure you create a [virtual environment](../virtual-environments.md){.internal-link target=_blank}, activate it, and then you can install the server application.

For example, to install Uvicorn:

<div class="termy">

eData":"2015-12-21T00:00:00","IssueTime":"1251","RPState":"CA","PlateExpiry":"200304","Make":"HOND","BodyStyle":"PA","Color":"GY","Location":"13147 WELBY WAY","Route":"01521","Agency":1,"ViolationCode":"4000A1","ViolationDescr":"NO EVIDENCE OF REG","Fine":50,"Latitude":99999,"Longitude":99999} {"Ticket":1103700150,"IssueData":"2015-12-21T00:00:00","IssueTime":"1435","RPState":"CA","PlateExpiry":"201512","Make":"GMC","BodyStyle":"VN","Color":"WH","Location":"525 S MAIN ST","Route":"1C51","Agency"...

 the version number 2.1.)

                            Preamble

  The licenses for most software are designed to take away your
freedom to share and change it.  By contrast, the GNU General Public
Licenses are intended to guarantee your freedom to share and change
free software--to make sure the software is free for all its users.

  This license, the Lesser General Public License, applies to some

{* ../../docs_src/body/tutorial001_py310.py hl[5:9] *}


The same as when declaring query parameters, when a model attribute has a default value, it is not required. Otherwise, it is required. Use `None` to make it just optional.

For example, this model above declares a JSON "`object`" (or Python `dict`) like:

```JSON
{
    "name": "Foo",
    "description": "An optional description",
    "price": 45.2,
    "tax": 3.5