///

/// tip

Notice that in this case we are using a standard Python `open()` function that interacts with a file.

So, it involves I/O (input/output), that requires "waiting" for things to be written to disk.

But `open()` doesn't use `async` and `await`.

So, we declare the event handler function with standard `def` instead of `async def`.

///

// rows in some manner. Requires all input rows to be processed,
// before a result is returned.
//
// Row function - An expression that depends on a value in the
// row. They have an output for each input row.
//
// Some types of a queries are not valid. For example, an aggregation
// function combined with a row function is meaningless ("AVG(s.Age) +

                return 42;
              }
            }));
  }

  public void testNullOutputStream() throws Exception {
    // create a null output stream
    OutputStream nos = ByteStreams.nullOutputStream();
    // write to the output stream
    nos.write('n');
    String test = "Test string for NullOutputStream";
    byte[] bytes = test.getBytes(US_ASCII);
    nos.write(bytes);

    static UnaryOperator<String> chain(UnaryOperator<String>... functions) {
        return chain(List.of(functions));
    }

    /**
     * Memoizes a given function that takes a String input and produces a String output.
     * This method creates a new function that caches the results of the original function,
     * improving performance for repeated calls with the same input.
     *

        generator.setCommandList(Collections.singletonList("echo test"));
        try {
            generator.generate("test_id", null);
            fail("Should throw exception for null output file");
        } catch (final Exception e) {
            assertTrue(true);
        }
    }

    @Test
    public void test_generate_thumbnailId_null() throws Exception {

  if stderr is None:
    stderr = sys.stdout
  if allow_non_zero:
    try:
      output = subprocess.check_output(cmd, stderr=stderr)
    except subprocess.CalledProcessError as e:
      output = e.output
  else:
    output = subprocess.check_output(cmd, stderr=stderr)
  return output.decode('UTF-8').strip()


def cygpath(path):
  """Convert path from posix to windows."""

Continuing with the previous example, it will be common to have more than one related model.

This is especially the case for user models, because:

* The **input model** needs to be able to have a password.
* The **output model** should not have a password.
* The **database model** would probably need to have a hashed password.

/// danger

Never store user's plaintext passwords. Always store a "secure hash" that you can then verify.

/// info

Added in FastAPI 0.134.0.

///

## Use Cases { #use-cases }

You could use this if you want to stream pure strings, for example directly from the output of an **AI LLM** service.

You could also use it to stream **large binary files**, where you stream each chunk of data as you read it, without having to read it all in memory at once.

	tagSet bool

	// Caching tags, only once
	cachedTags map[string]string
}

// MarshalXML - produces the xml representation of the Filter struct
// only one of Prefix, And and Tag should be present in the output.
func (f Filter) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if !f.set {
		return nil
	}

	if err := e.EncodeToken(start); err != nil {
		return err
	}

	switch {

     * This method constructs the command line arguments, sets up the classpath,
     * and launches the crawler as an external process. It handles process lifecycle,
     * monitors output, and ensures proper cleanup.
     *
     * @throws JobProcessingException if the crawler process fails or times out
     */
    protected void executeCrawler() {
        final List<String> cmdList = new ArrayList<>();