}

    @Test
    void testSetURLStreamHandlerFactory_ThrowsIllegalStateExceptionOnSecondAttempt() {
        // This test ensures that attempting to set the URLStreamHandlerFactory more than once
        // throws an IllegalStateException as per the contract.
        URLStreamHandlerFactory mockFactory1 = mock(URLStreamHandlerFactory.class);

```

That's all standard Python syntax for type declarations.

Use that same standard syntax for model attributes with internal types.

So, in our example, we can make `tags` be specifically a "list of strings":

{* ../../docs_src/body_nested_models/tutorial002_py310.py hl[12] *}

## Set types { #set-types }

But then we think about it, and realize that tags shouldn't repeat, they would probably be unique strings.

   * on {@link Platform} so that we can have different behavior in GWT.
   *
   * <p>This implementation tries to be smart in a number of ways. It recognizes cases where the
   * negation is cheaper to precompute than the matcher itself; it tries to build small hash tables
   * for matchers that only match a few characters, and so on. In the worst-case scenario, it

      assertWithMessage("quantile at index " + index)
          .that(percentiles().index(index).computeInPlace(dataset))
          .isWithin(ALLOWED_ERROR)
          .of(expectedLargeDatasetPercentile(index));
    }

    // Assert that the dataset contains the same elements after the in-place computation (although
    // they may be reordered). We only do this for one index rather than for all indexes, as it is

        return true;
      }
      if (object instanceof BooleanArrayAsList) {
        BooleanArrayAsList that = (BooleanArrayAsList) object;
        int size = size();
        if (that.size() != size) {
          return false;
        }
        for (int i = 0; i < size; i++) {
          if (array[start + i] != that.array[that.start + i]) {
            return false;
          }
        }
        return true;
      }

        assertWithMessage("roundToDouble(" + input + ", " + mode + ")")
            .that(BigIntegerMath.roundToDouble(input, mode))
            .isEqualTo(expectation);
      }

      if (!expectedValues.containsKey(UNNECESSARY)) {
        assertWithMessage("Expected roundUnnecessaryShouldThrow call")
            .that(unnecessaryShouldThrow)
            .isTrue();
        assertThrows(

      assertWithMessage("quantile at index " + index)
          .that(percentiles().index(index).computeInPlace(dataset))
          .isWithin(ALLOWED_ERROR)
          .of(expectedLargeDatasetPercentile(index));
    }

    // Assert that the dataset contains the same elements after the in-place computation (although
    // they may be reordered). We only do this for one index rather than for all indexes, as it is

        return true;
      }
      if (object instanceof BooleanArrayAsList) {
        BooleanArrayAsList that = (BooleanArrayAsList) object;
        int size = size();
        if (that.size() != size) {
          return false;
        }
        for (int i = 0; i < size; i++) {
          if (array[start + i] != that.array[that.start + i]) {
            return false;
          }
        }
        return true;
      }

### Required, can be `None` { #required-can-be-none }

You can declare that a parameter can accept `None`, but that it's still required. This would force clients to send a value, even if the value is `None`.

To do that, you can declare that `None` is a valid type but simply do not declare a default value:

{* ../../docs_src/query_params_str_validations/tutorial006c_an_py310.py hl[9] *}

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.