* @param <REP> The response type
     * @param req The request object used as the cache key
     * @param supplier The function to execute and cache the result
     * @return The result from the supplier (either fresh or cached)
     * @throws RuntimeException Any exception thrown by the supplier will be cached and re-thrown on subsequent calls
     */

Some requests will have a cached response. When this cached response isn’t fresh, OkHttp can do a _conditional GET_ to download an updated response if it’s newer than what’s cached. This requires headers like `If-Modified-Since` and `If-None-Match` to be added.

## Rewriting Responses

In this case, you can use `dict`:

{* ../../docs_src/extra_models/tutorial005_py310.py hl[6] *}

## Recap { #recap }

Use multiple Pydantic models and inherit freely for each case.

By the time I started creating **FastAPI** itself, most of the pieces were already in place, the design was defined, the requirements and tools were ready, and the knowledge about the standards and specifications was clear and fresh.

## Future { #future }

By this point, it's already clear that **FastAPI** with its ideas is being useful for many people.

It is being chosen over previous alternatives for suiting many use cases better.

    // a multithreaded environment for a couple of reasons:
    //
    // 1. Subscribers to events posted on different threads can be interleaved with each other
    //    freely. (A event on one thread, B event on another could yield any of
    //    [a1, a2, a3, b1, b2], [a1, b2, a2, a3, b2], [a1, b2, b3, a2, a3], etc.)

	Data []byte `msg:"d,allownil"` // optionally carries object data

	NumVersions      int       `msg:"nv"`
	SuccessorModTime time.Time `msg:"smt"`

	Fresh bool `msg:"fr"` // indicates this is a first time call to write FileInfo.

	// Position of this version or object in a multi-object delete call,
	// no other caller must set this value other than multi-object delete call.

      return this;
    }

    public <E> Interner<E> build() {
      if (!strong) {
        mapMaker.weakKeys();
      }
      return new InternerImpl<>(mapMaker);
    }
  }

  /** Returns a fresh {@link InternerBuilder} instance. */
  public static InternerBuilder newBuilder() {
    return new InternerBuilder();
  }

  /**

      return this;
    }

    public <E> Interner<E> build() {
      if (!strong) {
        mapMaker.weakKeys();
      }
      return new InternerImpl<>(mapMaker);
    }
  }

  /** Returns a fresh {@link InternerBuilder} instance. */
  public static InternerBuilder newBuilder() {
    return new InternerBuilder();
  }

  /**

    List<Object> equalArgs = new ArrayList<>(args);
    for (int i = 0; i < args.size(); i++) {
      Parameter param = params.get(i);
      Object arg = args.get(i);
      // Use new fresh value generator because 'args' were populated with new fresh generator each.
      // Two newFreshValueGenerator() instances should normally generate equal value sequence.
      Object shouldBeEqualArg = generateDummyArg(param, newFreshValueGenerator());

	// red banner along with the error message. Since the error
	// message itself contains some colored text, we needed
	// to use some ANSI control escapes to cursor color state
	// and freely move in the screen.
	for line := range strings.SplitSeq(errMsg, "\n") {
		if len(line) == 0 {
			// No more text to print, just quit.
			break
		}

		// Save the attributes of the current cursor helps