for item in items:
        yield item
```

## Server-Sent Events (SSE)

To stream Server-Sent Events, use `response_class=EventSourceResponse` and `yield` items from the endpoint.

Plain objects are automatically JSON-serialized as `data:` fields, declare the return type so the serialization is done by Pydantic:

```python
from collections.abc import AsyncIterable

from fastapi import FastAPI

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       *
       * Example:
       * ```
       * --> POST /greeting http/1.1
       * Host: example.com
       * Content-Type: plain/text
       * Content-Length: 3
       * --> END POST
       *
       * <-- 200 OK (22ms)
       * Content-Type: plain/text
       * Content-Length: 6
       * <-- END HTTP
       * ```
       */
      HEADERS,

      /**

        });

        mimeTypeHelper.init();

        // Null config means no override
        try (InputStream is = new ByteArrayInputStream("Hello world".getBytes(StandardCharsets.UTF_8))) {
            assertEquals("text/plain", mimeTypeHelper.getContentType(is, "test.txt"));
        }
    }

    @Test
    public void test_init_singleMapping() throws IOException {
        ComponentUtil.setFessConfig(new FessConfig.SimpleImpl() {

/** A utility method to perform unchecked casts to suppress errors produced by nullness analyses. */
@GwtCompatible
final class NullnessCasts {
  /**
   * Accepts a {@code @Nullable T} and returns a plain {@code T}, without performing any check that
   * that conversion is safe.
   *
   * <p>This method is intended to help with usages of type parameters that have {@linkplain

/** A utility method to perform unchecked casts to suppress errors produced by nullness analyses. */
@GwtCompatible
final class NullnessCasts {
  /**
   * Accepts a {@code @Nullable T} and returns a plain {@code T}, without performing any check that
   * that conversion is safe.
   *
   * <p>This method is intended to help with usages of type parameters that have {@linkplain

        file("consumer/build/archives/elasticsearch.tar.gz").exists()

        when:
        result = gradleRunner("copyDir", "-Pversion=1.0").build()
        then: "plain copy task executed and target folder contains plain content"
        result.task(':buildProducer').outcome == TaskOutcome.SUCCESS
        result.task(':consumer:copyDir').outcome == TaskOutcome.SUCCESS
        file("producer-tar/build/install/someFile.txt").exists()

      |Content-Disposition: form-data; name="files"
      |Content-Type: multipart/mixed; boundary=BbC04y
      |
      |--BbC04y
      |Content-Disposition: file; filename="file1.txt"
      |Content-Type: text/plain; charset=utf-8
      |
      |... contents of file1.txt ...
      |--BbC04y
      |Content-Disposition: file; filename="file2.gif"
      |Content-Transfer-Encoding: binary
      |Content-Type: image/gif
      |

        .body(
          """
          |data: hey
          |
          |
          """.trimMargin(),
        ).setHeader("content-type", "text/plain")
        .build(),
    )
    newEventSource()
    listener.assertFailure("Invalid content-type: text/plain")
  }

  @Test
  fun badResponseCode() {
    server.enqueue(
      MockResponse
        .Builder()
        .body(
          """

image/x-xwindowdump            xwd              #
text/css                       css              # Cascading Style Sheet
text/html                      html htm         # HTML Document
text/plain                     txt ini log in cfg m4 sh     # Plain Text File
text/richtext                  rtx              # Rich Text File
text/tab-separated-values      tsv              #
text/x-setext                  etx              #