It might be useful, for example, to return custom headers or cookies.

## Return a `Response`

In fact, you can return any `Response` or any sub-class of it.

!!! tip
    `JSONResponse` itself is a sub-class of `Response`.

And when you return a `Response`, **FastAPI** will pass it directly.

It won't do any data conversion with Pydantic models, it won't convert the contents to any type, etc.

        final LineIterator it = new LineIterator(reader);
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("aaa"));
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("bbb"));
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("ccc"));
        assertThat(it.hasNext(), is(not(true)));
    }

    /**

        // For Java compilation incremental analysis
        "it.unimi.dsi.fastutil.ints.IntOpenHashSet",
        "it.unimi.dsi.fastutil.ints.IntSets",
        // For the embedded Kotlin compiler
        "it.unimi.dsi.fastutil.ints.Int2ObjectMap",
        "it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap",
        "it.unimi.dsi.fastutil.objects.Object2IntMap",
        "it.unimi.dsi.fastutil.objects.Object2IntOpenHashMap",

```

</div>

It is **HIGHLY encouraged** that you write or copy the code, edit it and run it locally.

Using it in your editor is what really shows you the benefits of FastAPI, seeing how little code you have to write, all the type checks, autocompletion, etc.

---

## Install FastAPI

The first step is to install FastAPI.

For the tutorial, you might want to install it with all the optional dependencies and features:

        allTestedVersions = testedVersions.map { VersionNumber.parse(it.gradleVersion().version) }
            .groupBy { "${it.major}.${it.minor}" }
            .map { (_, v) -> v.maxOrNull()!!.format() }

        // Limit to first and last release of each major version
        mainTestedVersions = testedVersions.map { VersionNumber.parse(it.gradleVersion().version) }
            .groupBy { it.major }

        return contributorLines
            .map { it.trim() }
            .filter { it.isNotEmpty() }
            .onEach { if (!contributorLineRegex.containsMatchIn(it)) throw IllegalStateException("Invalid contributor line: $it") }
            .map { GitHubUser(contributorLineRegex.find(it)!!.groupValues[2], contributorLineRegex.find(it)!!.groupValues[1]) }
            .toSet()
    }

    /**

                parameters.testPathToBinaryResultsDirs = allTasks.filterIsInstance<Test>().associate { it.path to it.binaryResultsDirectory.get().asFile }

                val taskPathToReports = ******@****.***ks
                    .associate { it.path to it.genericHtmlReports() + it.findTraceJson() }
                    .filter { it.value.isNotEmpty() }

// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of

  val call = okHttpClient.newCall(Request(url.toHttpUrl()))

  val suites =
    call.executeAsync().use {
      if (!it.isSuccessful) {
        throw IOException("Failed ${it.code} ${it.message}")
      }
      it.body.string().lines()
        .mapNotNull { parseIanaCsvRow(it) }
    }

  return IanaSuites("current", suites)

                    it as KtPsiDiagnosticWithParameters2<*, *>,
                    token,
                    convertArgument(it.a, this),
                    convertArgument(it.b, this)
                )
            }
            is KtDiagnosticFactory3<*, *, *> -> KtFirDiagnostic3Creator<Any?, Any?, Any?> {
                KtCompilerPluginDiagnostic3Impl(
                    it as KtPsiDiagnosticWithParameters3<*, *, *>,