Both are equivalent and underneath they are the same, but I would recommend `Union` instead of `Optional` because the word "**optional**" would seem to imply that the value is optional, and it actually means "it can be `None`", even if it's not optional and is still required.

I think `Union[SomeType, None]` is more explicit about what it means.

It's just about the words and names. But those words can affect how you and your teammates think about the code.

    if (value < 0) {
      throw new IllegalArgumentException(name + " cannot be negative but was: " + value);
    }
    return value;
  }

  @CanIgnoreReturnValue
  static long checkNonnegative(long value, String name) {
    if (value < 0) {
      throw new IllegalArgumentException(name + " cannot be negative but was: " + value);
    }
    return value;
  }

  static void checkPositive(int value, String name) {

Create file parameters the same way you would for `Body` or `Form`:

{* ../../docs_src/request_files/tutorial001_an_py310.py hl[9] *}

/// info

`File` is a class that inherits directly from `Form`.

But remember that when you import `Query`, `Path`, `File` and others from `fastapi`, those are actually functions that return special classes.

///

/// tip

  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addEdge(N1, N2, E13);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test

  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addEdge(N1, N2, E13);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test

		if fi.VersionID != versions[i].VersionID {
			t.Fatalf("getFileInfoVersions: versions don't match at %d, version id expected %s but got %s", i, fi.VersionID, versions[i].VersionID)
		}
		if fi.NumVersions != len(fivs.Versions) {
			t.Fatalf("getFileInfoVersions: version with %s version id expected to have %d as NumVersions but got %d", fi.VersionID, len(fivs.Versions), fi.NumVersions)
		}
	}

	for i, free := range fivs.FreeVersions {

///

## OpenAPI and API docs { #openapi-and-api-docs }

If you return additional status codes and responses directly, they won't be included in the OpenAPI schema (the API docs), because FastAPI doesn't have a way to know beforehand what you are going to return.

Just functions that look the same as the *path operation functions*.

But still, it is very powerful, and allows you to declare arbitrarily deeply nested dependency "graphs" (trees).

/// tip

All this might not seem as useful with these simple examples.

But you will see how useful it is in the chapters about **security**.

And you will also see the amounts of code it will save you.

* `compresslevel` - Used during GZip compression. It is an integer ranging from 1 to 9. Defaults to `9`. Lower value results in faster compression but larger file sizes, while higher value results in slower compression but smaller file sizes.

## Other middlewares { #other-middlewares }

There are many other ASGI middlewares.

For example:

    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testReplaceEntry_unsupportedAbsentKey() {
    try {
      getMap().replace(k3(), v3(), v4());
    } catch (UnsupportedOperationException tolerated) {
      // the operation would be a no-op, so exceptions are allowed but not required
    }
    expectUnchanged();