* You can then further modify the `response` before returning it.

{* ../../docs_src/middleware/tutorial001_py310.py hl[8:9,11,14] *}

/// tip

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

    canceled = true
    stream?.closeLater(ErrorCode.CANCEL)
  }

  companion object {
    private const val CONNECTION = "connection"
    private const val HOST = "host"
    private const val KEEP_ALIVE = "keep-alive"
    private const val PROXY_CONNECTION = "proxy-connection"
    private const val TRANSFER_ENCODING = "transfer-encoding"
    private const val TE = "te"
    private const val ENCODING = "encoding"

import java.util.Set;
import java.util.TreeSet;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import javax.inject.Inject;

/**
 * Once a minor release has happened, we no longer need to keep the changelog files that went into
 * that release in the development branch for that major series or the branch for the next major
 * series
 * <p>

      }
    }

    /**
     * Associates {@code key} with {@code value} in the built map. If the same key is put more than
     * once, {@link #buildOrThrow} will fail, while {@link #buildKeepingLast} will keep the last
     * value put for that key.
     */
    @CanIgnoreReturnValue
    public Builder<K, V> put(K key, V value) {
      ensureCapacity(size + 1);
      Entry<K, V> entry = entryOf(key, value);

{* ../../docs_src/server_sent_events/tutorial005_py310.py hl[14] *}

## Détails techniques { #technical-details }

FastAPI met en œuvre certaines bonnes pratiques SSE prêtes à l’emploi.

                return host + "/"; // mimic the JVM behaviour for root or server
            }
            if (path.endsWith("/")) {
                return path.substring(0, path.length()); // keep trailing slash
            }
            String[] parts = path.split("/");
            return parts[parts.length - 1];
        }

        @Override
        public String getParent() {

Let's continue from the previous example. We wanted to **annotate the function with one type**, but we wanted to be able to return from the function something that actually includes **more data**.

We want FastAPI to keep **filtering** the data using the response model. So that even though the function returns more data, the response will only include the fields declared in the response model.

            sb.append("\"field").append(i).append("\"");
        }

        String[] result = KuromojiCSVUtil.parse(sb.toString());
        assertEquals(1000, result.length);
        // Quoted values keep their quotes
        for (int i = 0; i < 999; i++) {
            assertEquals("field" + i, result[i]);
        }
        assertEquals("\"field999\"", result[999]);

    }

    @Test

        a full-time Guava team member. [Feedback](https://stackoverflow.com/a/4543114) from our
        users indicates that they really appreciate Guava's high power-to-weight ratio. It's
        important to us to keep Guava as easy to use and understand as we can. That means boiling
        features down to compact but powerful abstractions, and controlling feature bloat carefully.

Just use any kind of model, any kind of class, any kind of database that you need for your application. **FastAPI** has you covered with the dependency injection system.

## Code size { #code-size }

This example might seem verbose. Keep in mind that we are mixing security, data models, utility functions and *path operations* in the same file.

But here's the key point.

The security and dependency injection stuff is written once.