async def stream_image() -> AsyncIterable[bytes]:
    with read_image() as image_file:
        for chunk in image_file:
            yield chunk


@app.get("/image/stream-no-async", response_class=PNGStreamingResponse)
def stream_image_no_async() -> Iterable[bytes]:
    with read_image() as image_file:
        for chunk in image_file:
            yield chunk


@app.get("/image/stream-no-async-yield-from", response_class=PNGStreamingResponse)

    for (int chunk : CHUNK_SIZES) {
      chunk = max(1, min(chunk, input.length()));
      assertEquals(expectProcess, bufferHelper(input, chunk));
      assertEquals(expectRead, readUsingJava(input, chunk));
      assertEquals(expectRead, readUsingReader(input, chunk, true));
      assertEquals(expectRead, readUsingReader(input, chunk, false));
    }
  }

 */
@FunctionalInterface
public interface LlmStreamCallback {

    /**
     * Called for each chunk of the streaming response.
     *
     * @param chunk the text chunk from the LLM response
     * @param done true if this is the final chunk
     */
    void onChunk(String chunk, boolean done);

    /**
     * Called when an error occurs during streaming.
     *

      if (closed) return
      closed = true
      detachTimeout(timeout)
      state = STATE_READ_RESPONSE_HEADERS
    }
  }

  /**
   * An HTTP body with alternating chunk sizes and chunk bodies. It is the caller's responsibility
   * to buffer chunks; typically by using a buffered sink with this sink.
   */
  private inner class ChunkedSink : Sink {

     *
     * @param phase the phase name that completed
     */
    void onPhaseComplete(String phase);

    /**
     * Called when a chunk of the response is available during streaming.
     *
     * @param content the content chunk
     * @param done true if this is the final chunk
     */
    void onChunk(String content, boolean done);

    /**
     * Called when an error occurs during processing.
     *

                callback.onPhaseStart(ChatPhaseCallback.PHASE_ANSWER, "Generating response...");
                llmClientManager.generateUnclearIntentResponse(userMessage, history, (chunk, done) -> {
                    fullResponse.append(chunk);
                    callback.onChunk(chunk, done);
                });
                callback.onPhaseComplete(ChatPhaseCallback.PHASE_ANSWER);
                if (logger.isDebugEnabled()) {

                events.add("complete:" + phase);
            }

            @Override
            public void onChunk(String content, boolean done) {
                events.add("chunk:" + content + ":" + done);
            }

            @Override
            public void onError(String phase, String errorMessage) {
                events.add("error:" + phase + ":" + errorMessage);
            }

      for (int remaining = len; remaining >= 3; remaining -= 3) {
        int chunk = (bytes[i++] & 0xFF) << 16 | (bytes[i++] & 0xFF) << 8 | (bytes[i++] & 0xFF);
        target.append(alphabet.encode(chunk >>> 18));
        target.append(alphabet.encode((chunk >>> 12) & 0x3F));
        target.append(alphabet.encode((chunk >>> 6) & 0x3F));
        target.append(alphabet.encode(chunk & 0x3F));
      }
      if (i < off + len) {

If you declare a `response_class=StreamingResponse` in your *path operation function*, you can use `yield` to send each chunk of data in turn.

{* ../../docs_src/stream_data/tutorial001_py310.py ln[1:23] hl[20,23] *}

FastAPI will give each chunk of data to the `StreamingResponse` as is, it won't try to convert it to JSON or anything similar.

### Non-async *path operation functions* { #non-async-path-operation-functions }

        final PrintWriter writer = new PrintWriter(stringWriter);

        chatApiManager.sendSseEvent(writer, "chunk", Map.of("content", "Hello "));

        final String output = stringWriter.toString();
        assertTrue(output.contains("event: chunk"));
        assertTrue(output.contains("\"content\":\"Hello \""));
    }

    @Test
    public void test_sendSseEvent_error() {