Primero enfoquémonos en la dependencia.

Es solo una función que puede tomar todos los mismos parámetros que una *path operation function* puede tomar:

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

Eso es todo.

**2 líneas**.

Y tiene la misma forma y estructura que todas tus *path operation functions*.

Puedes pensar en ella como una *path operation function* sin el "decorador" (sin el `@app.get("/some-path")`).

/**
 * Functional interface for boolean functions.
 * Represents a function that accepts one argument and produces a boolean result.
 * @param <T> the type of the input to the function
 */
@FunctionalInterface
public interface BooleanFunction<T> {
    /**
     * Applies this function to the given argument.
     * @param t the function argument
     * @return the function result
     */
    boolean apply(T t);

import static com.google.common.truth.Truth.assertThat;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.testing.MapInterfaceTest;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import java.util.HashMap;
import java.util.Map;
import org.jspecify.annotations.NullMarked;

/**
 * Tests for {@link Maps#transformValues(Map, Function)}.
 *
 * @author Isaac Shum
 */
@GwtCompatible
@NullMarked

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import java.util.SortedMap;
import org.jspecify.annotations.NullMarked;

/**
 * Tests for {@link Maps#transformValues(SortedMap, Function)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@NullMarked

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.stream.Collector;
import org.jspecify.annotations.Nullable;

/**
 * A {@link Table} whose contents will never change, with many other important properties detailed

Lkotlin/jvm/functions/Function1;
Lkotlin/jvm/functions/Function20;
Lkotlin/jvm/functions/Function21;
Lkotlin/jvm/functions/Function22;
Lkotlin/jvm/functions/Function2;
Lkotlin/jvm/functions/Function3;
Lkotlin/jvm/functions/Function4;
Lkotlin/jvm/functions/Function5;
Lkotlin/jvm/functions/Function6;
Lkotlin/jvm/functions/Function7;
Lkotlin/jvm/functions/Function8;
Lkotlin/jvm/functions/Function9;
Lkotlin/jvm/internal/ArrayIterator;

Then you can create another dependency function (a "dependable") that at the same time declares a dependency of its own (so it is a "dependant" too):

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[13] *}

Let's focus on the parameters declared:

* Even though this function is a dependency ("dependable") itself, it also declares another dependency (it "depends" on something else).

# Request Parameters

Here's the reference information for the request parameters.

These are the special functions that you can put in *path operation function* parameters or dependency functions with `Annotated` to get data from the request.

It includes:

* `Query()`
* `Path()`
* `Body()`
* `Cookie()`
* `Header()`
* `Form()`
* `File()`

You can import them all directly from `fastapi`:

```python

/// note | Technical Details

When you import `Query`, `Path` and others from `fastapi`, they are actually functions.

That when called, return instances of classes of the same name.

So, you import `Query`, which is a function. And when you call it, it returns an instance of a class also named `Query`.

These functions are there (instead of just using the classes directly) so that your editor doesn't mark errors about their types.