## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

For many scenarios, you can handle security (authorization, authentication, etc.) with dependencies, using `Depends()`.

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package okhttp3

import java.io.IOException
import java.security.Security
import okhttp3.internal.platform.Platform
import org.conscrypt.Conscrypt

// TLS 1.3
private val TLS13_CIPHER_SUITES =
  listOf(
    CipherSuite.TLS_AES_128_GCM_SHA256,
    CipherSuite.TLS_AES_256_GCM_SHA384,

# Header Parameters { #header-parameters }

You can define Header parameters the same way you define `Query`, `Path` and `Cookie` parameters.

## Import `Header` { #import-header }

First import `Header`:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## Declare `Header` parameters { #declare-header-parameters }

Then declare the header parameters using the same structure as with `Path`, `Query` and `Cookie`.

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.repository.legacy.metadata;

import java.util.List;

import org.apache.maven.artifact.Artifact;
import org.apache.maven.artifact.repository.ArtifactRepository;
import org.apache.maven.artifact.repository.RepositoryRequest;

/**
 * Forms a request to retrieve artifact metadata.
 *
 */
@Deprecated

 */
package org.codelibs.core.lang;

import static org.codelibs.core.collection.ArrayUtil.asArray;
import static org.codelibs.core.misc.AssertionUtil.assertArgumentNotNull;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;

import org.codelibs.core.exception.ClIllegalArgumentException;
import org.codelibs.core.exception.IllegalAccessRuntimeException;

/**

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package jcifs.internal.witness;

import java.io.IOException;
import java.net.InetAddress;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import jcifs.CIFSContext;
import jcifs.dcerpc.DcerpcHandle;

/**
 * Client implementation for the SMB Witness RPC protocol (MS-SWN).

 * limitations under the License.
 */

package com.google.common.collect.testing;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.features.CollectionSize;
import java.util.Collection;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**

 * limitations under the License.
 */

package com.google.common.eventbus.outside;

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

import com.google.common.eventbus.Subscribe;
import com.google.common.eventbus.outside.BaseSubscriberFinderTest.Subscriber;
import java.util.ArrayList;
import java.util.List;

public class BaseSubscriberFinderTest extends AbstractEventBusTest<Subscriber> {

 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.testing.SampleElements.Unhashables;
import com.google.common.collect.testing.UnhashableObject;
import java.util.Map;
import org.jspecify.annotations.NullUnmarked;

@GwtIncompatible // GWT's ImmutableMap emulation is backed by java.util.HashMap.

 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.collect.Tables.unmodifiableTable;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.TableCollectionTest.RowTests;
import java.util.Map;
import org.jspecify.annotations.NullMarked;

@GwtCompatible
@NullMarked