/**
 * A subscriber method on a specific object, plus the executor that should be used for dispatching
 * events to it.
 *
 * <p>Two subscribers are equivalent when they refer to the same method on the same object (not
 * class). This property is used to ensure that no subscriber method is registered more than once.
 *
 * @author Colin Decker
 */
@ElementTypesAreNonnullByDefault
class Subscriber {

### Tags with Enums

If you have a big application, you might end up accumulating **several tags**, and you would want to make sure you always use the **same tag** for related *path operations*.

In these cases, it could make sense to store the tags in an `Enum`.

**FastAPI** supports that the same way as with plain strings:

```Python hl_lines="1  8-10  13  18"
{!../../docs_src/path_operation_configuration/tutorial002b.py!}
```

     *
     * <p>This method is used when testing iterators without a known ordering. We poll the target
     * iterator's next element and pass it to the reference iterator through this method so it can
     * return the same element. This enables the assertion to pass and the reference iterator to
     * properly update its state.
     */
    void promoteToNext(E e) {
      if (nextElements.remove(e)) {
        nextElements.push(e);

		{[]string{"https://localhost:9000/d1", "https://localhost:9001/d2", "https://localhost:9002/d3", "https://localhost:9003/d4"}, nil},
		// // It is valid WRT endpoint list that same path is expected with different port on same server.
		{[]string{"https://127.0.0.1:9000/d1", "https://127.0.0.1:9001/d1", "https://127.0.0.1:9002/d1", "https://127.0.0.1:9003/d1"}, nil},

        return new IllegalArgumentException(
            "Multiple entries with same key: " + key + "=" + value1 + " and " + key + "=" + value2);
      }
    }
  }

  /**
   * Returns an immutable map containing the same entries as {@code map}. The returned map iterates
   * over entries in the same order as the {@code entrySet} of the original map. If {@code map}

<pre>
[...]Point{{1.5, -3.5}, {0, 0}}     // same as [...]Point{Point{1.5, -3.5}, Point{0, 0}}
[][]int{{1, 2, 3}, {4, 5}}          // same as [][]int{[]int{1, 2, 3}, []int{4, 5}}
[][]Point{{{0, 1}, {1, 2}}}         // same as [][]Point{[]Point{Point{0, 1}, Point{1, 2}}}
map[string]Point{"orig": {0, 0}}    // same as map[string]Point{"orig": Point{0, 0}}
map[Point]string{{0, 0}: "orig"}    // same as map[Point]string{Point{0, 0}: "orig"}

///

### Create the `Settings` object

Import `BaseSettings` from Pydantic and create a sub-class, very much like with a Pydantic model.

The same way as with Pydantic models, you declare class attributes with type annotations, and possibly default values.

You can use all the same validation features and tools you use for Pydantic models, like different data types and additional validations with `Field()`.

//// tab | Pydantic v2

                should have all the fields, including the ones that have the same value
                as the default. This is different from `response_model_exclude_unset`
                in that if the fields are set but contain the same default values,
                they will be excluded from the response.

  abstract int distinctElements();

  // Object methods

  /**
   * {@inheritDoc}
   *
   * <p>This implementation returns {@code true} if {@code object} is a multiset of the same size
   * and if, for each element, the two multisets have the same count.
   */
  @Override
  public final boolean equals(@CheckForNull Object object) {
    return Multisets.equalsImpl(this, object);
  }

  /**
   * {@inheritDoc}

   * exactly one entry for each distinct element in the multiset (thus it always has the same size
   * as the {@link #elementSet}). The order of the elements in the element set is unspecified.
   *
   * <p>The entry set is backed by the same data as the multiset, so any change to either is
   * immediately reflected in the other. However, multiset changes may or may not be reflected in