Let's first focus on the dependency.

It is just a function that can take all the same parameters that a *path operation function* can take:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

That's it.

**2 lines**.

And it has the same shape and structure that all your *path operation functions* have.

You can think of it as a *path operation function* without the "decorator" (without the `@app.get("/some-path")`).

  private static <T> void testSuccessfulForwarding(
      Class<T> interfaceType, Method method, Function<? super T, ? extends T> wrapperFunction) {
    new InteractionTester<T>(interfaceType, method).testInteraction(wrapperFunction);
  }

  private static <T> void testExceptionPropagation(
      Class<T> interfaceType, Method method, Function<? super T, ? extends T> wrapperFunction) {
    RuntimeException exception = new RuntimeException();

 */

package com.google.common.util.concurrent;

import com.google.common.base.Function;
import java.util.concurrent.Executor;
import org.jspecify.annotations.Nullable;

/**
 * Hidden superclass of {@link Futures} that provides us a place to declare special GWT versions of
 * the {@link Futures#catching(ListenableFuture, Class, com.google.common.base.Function)
 * Futures.catching} family of methods. Those versions have slightly different signatures.

   * Not supported. Use {@link #toImmutableBiMap} instead. This method exists only to hide {@link
   * ImmutableMap#toImmutableMap(Function, Function)} from consumers of {@code ImmutableBiMap}.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Use {@link ImmutableBiMap#toImmutableBiMap(Function, Function)}.
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */
  @Deprecated
  @DoNotCall("Use toImmutableBiMap")

// Cache contains a synchronized value that is considered valid
// for a specific amount of time.
// An Update function must be set to provide an updated value when needed.
type Cache[T any] struct {
	// updateFn must return an updated value.
	// If an error is returned the cached value is not set.
	// Only one caller will call this function at any time, others will be blocking.
	// The returned value can no longer be modified once returned.

   *
   * <p>Equivalent to {@link #binarySearch(List, Object, Comparator, KeyPresentBehavior,
   * KeyAbsentBehavior)} using {@link Lists#transform(List, Function) Lists.transform(list,
   * keyFunction)}.
   */
  public static <E extends @Nullable Object, K extends @Nullable Object> int binarySearch(
      List<E> list,
      Function<? super E, K> keyFunction,
      @ParametricNullness K key,

///

### Step 4: define the **path operation function** { #step-4-define-the-path-operation-function }

This is our "**path operation function**":

* **path**: is `/`.
* **operation**: is `get`.
* **function**: is the function below the "decorator" (below `@app.get("/")`).

{* ../../docs_src/first_steps/tutorial001_py39.py hl[7] *}

This is a Python function.

### Dependencies with `yield` and `scope` { #dependencies-with-yield-and-scope }

In version 0.121.0, FastAPI added support for `Depends(scope="function")` for dependencies with `yield`.

Using `Depends(scope="function")`, the exit code after `yield` is executed right after the *path operation function* is finished, before the response is sent back to the client.

// or a function call.
type PrimaryTerm struct {
	Value         *LitValue   `parser:"  @@"`
	JPathExpr     *JSONPath   `parser:"| @@"`
	ListExpr      *ListExpr   `parser:"| @@"`
	SubExpression *Expression `parser:"| \"(\" @@ \")\""`
	// Include function expressions here.
	FuncCall *FuncExpr `parser:"| @@"`
}

// FuncExpr represents a function call
type FuncExpr struct {

  @Override
  public Set<T> asSet() {
    return Collections.singleton(reference);
  }

  @Override
  public <V> Optional<V> transform(Function<? super T, V> function) {
    return new Present<>(
        checkNotNull(
            function.apply(reference),
            "the Function passed to Optional.transform() must not return null."));
  }

  @Override
  public boolean equals(@Nullable Object obj) {