We see that we are going to need some dependencies used in several places of the application.

So we put them in their own `dependencies` module (`app/dependencies.py`).

We will now use a simple dependency to read a custom `X-Token` header:

{* ../../docs_src/bigger_applications/app_an_py39/dependencies.py hl[3,6:8] title["app/dependencies.py"] *}

/// tip

We are using an invented header to simplify this example.

    - [Additional Notable Feature Updates](#additional-notable-feature-updates)
  - [Known Issues](#known-issues)
  - [Urgent Upgrade Notes](#urgent-upgrade-notes)
    - [(No, really, you MUST read this before you upgrade)](#no-really-you-must-read-this-before-you-upgrade)
      - [API Machinery](#api-machinery)
      - [Apps](#apps)
      - [Auth](#auth)
      - [AWS](#aws)
      - [Azure](#azure)
      - [CLI](#cli)

e(this,i),n.default(this).data(S,a)),"undefined"===a[t])throw new Error(t+" is not a function");a[t]()}))},e}();n.default(document).on("click",H,(function(e){e.preventDefault(),M._jQueryInterface.call(n.default(this),"toggle")})),n.default(document).ready((function(){M._jQueryInterface.call(n.default(H),"_init")})),n.default.fn[T]=M._jQueryInterface,n.default.fn[T].Constructor=M,n.default.fn[T].noConflict=function(){return n.default.fn[T]=j,M._jQueryInterface};var q="DirectChat",O="lte.directchat",...

        Build build = getModel().getBuild();
        return build != null ? build : Build.newInstance();
    }

    /**
     * Returns the path to the pom file for this project.
     * A project is usually read from a file named {@code pom.xml},
     * which contains the {@linkplain #getModel() model} in an XML form.
     * When a custom {@code org.apache.maven.api.spi.ModelParser} is used,
     * the path may point to a non XML file.

        response.setContentCache(cache);

        try (InputStream stream = response.getContentAsStream()) {
            assertNotNull(stream);
            byte[] buffer = new byte[1024];
            int bytesRead = stream.read(buffer);
            assertEquals(data.length, bytesRead);
            assertArrayEquals(data, Arrays.copyOf(buffer, bytesRead));
        }
    }

    @Test
    public void testGetContentAsStreamWithoutCache() {

            try {
                Map<String, ?> options = Collections.singletonMap(MetadataReader.IS_STRICT, Boolean.FALSE);

                Metadata pluginGroupMetadata =
                        metadataReader.read(metadata.getPath().toFile(), options);

                List<org.apache.maven.artifact.repository.metadata.Plugin> plugins = pluginGroupMetadata.getPlugins();

                if (plugins != null) {

//     compress: true # S2/Snappy compressed archive
//     smallerThan: 5MiB # create archive for all objects smaller than 5MiB
//     skipErrs: false # skips any source side read() errors

// BatchJobSnowball describes the snowball feature when replicating objects from a local source to a remote target
type BatchJobSnowball struct {
	line, col   int

	var sub *subHandlerID
	if m.Payload == nil {
		m.Payload = GetByteBuffer()[:0]
	}
	h, err := m.UnmarshalMsg(b)
	if err != nil {
		return nil, nil, fmt.Errorf("read write: %v", err)
	}
	if len(m.Payload) == 0 && m.Flags&FlagPayloadIsZero == 0 {
		PutByteBuffer(m.Payload)
		m.Payload = nil
	}
	if m.Flags&FlagCRCxxh3 != 0 {
		const hashLen = 4
		if len(h) < hashLen {

					return nil, err
				}
			case 1, 2:
				v, b, err := msgp.ReadBytesZC(b)
				if err != nil {
					return nil, err
				}
				if _, nbuf, err := msgp.ReadUint32Bytes(b); err == nil {
					// Read metadata CRC (added in v2, ignore if not found)
					b = nbuf
				}

				_, err = msgp.CopyToJSON(buf, bytes.NewReader(v))
				if err != nil {
					return nil, err
				}
				data = b
			case 3:

            try {
                model = modelProcessor.read(modelSource.getInputStream(), options);
            } catch (ModelParseException e) {
                if (!strict) {
                    throw e;
                }

                options.put(ModelProcessor.IS_STRICT, Boolean.FALSE);

                try {
                    model = modelProcessor.read(modelSource.getInputStream(), options);