Then set Cookies in it, and then return it:

{* ../../docs_src/response_cookies/tutorial001_py310.py hl[10:12] *}

/// tip

Keep in mind that if you return a response directly instead of using the `Response` parameter, FastAPI will return it directly.

And as the `Response` can be used frequently to set headers and cookies, **FastAPI** also provides it at `fastapi.Response`.

///

## Custom Headers { #custom-headers }

Keep in mind that custom proprietary headers can be added [using the `X-` prefix](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers).

    App->>Client: Send Item 2
    App->>App: Produce Item 3
    Client->>Client: Process Item 2
    App->>Client: Send Item 3
    Client->>Client: Process Item 3
    Note over App: Keeps producing...
    Note over Client: Keeps consuming...
```

它甚至可以是一个无限流，你可以一直持续发送数据。

## JSON Lines { #json-lines }

在这些场景中，常见的做法是发送 “JSON Lines”，这是一种每行发送一个 JSON 对象的格式。

 *
 * <p>This class can't depend on other Guava code. If we were to load this class in the same class
 * loader as the rest of Guava, this thread would keep an indirect strong reference to the class
 * loader and prevent it from being garbage collected. This poses a problem for environments where

          sb.append(DELIMITER_STRING);
        }
        sb.append(comp);
      }
      dummy ^= sb.toString().length();
    }
    return dummy;
  }

  /**
   * Similar to the above, but keeps a boolean flag rather than checking for the string accumulated
   * so far being empty. As a result, it does not have the above-mentioned bug.
   */
  @Benchmark
  int booleanIfFirst(int reps) {
    int dummy = 0;

            call.executeAsync()
          }
        }
      }

      assertThat(call.canceled).isTrue()
      assertThat(call.responseClosed).isTrue()
    }
  }

  /** A call that keeps track of whether its response body is closed. */
  private class ClosableCall : FailingCall() {
    private val response =
      Response
        .Builder()
        .request(Request("https://example.com/".toHttpUrl()))

            }

            // this has to be a separate "if" statement, to capture the case of: "-Dfoo=bar"
            if (addedToBuffer && arg.endsWith("\"")) {
                // if we're building an argument, keep doing so.
                // if this is the case of "-Dfoo=bar", then we need to adjust the buffer.
                if (!currentArg.isEmpty()) {
                    currentArg.setLength(currentArg.length() - 1);
                }

### We Make Mistakes { #we-make-mistakes }

We, as humans, make **mistakes**, all the time. Software almost *always* has **bugs** hidden in different places. 🐛

And we as developers keep improving the code as we find those bugs and as we implement new features (possibly adding new bugs too 😅).

### Small Errors Automatically Handled { #small-errors-automatically-handled }

          sb.append(DELIMITER_STRING);
        }
        sb.append(comp);
      }
      dummy ^= sb.toString().length();
    }
    return dummy;
  }

  /**
   * Similar to the above, but keeps a boolean flag rather than checking for the string accumulated
   * so far being empty. As a result, it does not have the above-mentioned bug.
   */
  @Benchmark
  int booleanIfFirst(int reps) {
    int dummy = 0;

   - Rebase to tidy commits before submitting (e.g., `git rebase -i main` to squash typos or reword messages), unless multiple contributors worked on the branch.
   - Keep PRs focused—one feature or fix. Split large changes into multiple PRs.

3. **Testing**:
   - Include unit tests for new functionality or bug fixes.
   - Ensure existing tests pass (`make test`).