If you pass a "callable" as a dependency in **FastAPI**, it will analyze the parameters for that "callable", and process them in the same way as the parameters for a *path operation function*. Including sub-dependencies.

That also applies to callables with no parameters at all. The same as it would be for *path operation functions* with no parameters.

That configuration would change the syntax highlighting color theme:

<img src="/img/tutorial/extending-openapi/image04.png">

## Change Default Swagger UI Parameters

FastAPI includes some default configuration parameters appropriate for most of the use cases.

It includes these default configurations:

{* ../../fastapi/openapi/docs.py ln[8:23] hl[17:23] *}

        this.hostname = value;
    }

    public String getParameters() {
        checkSpecifiedProperty("parameters");
        return convertEmptyToNull(parameters);
    }

    public void setParameters(String value) {
        registerModifiedProperty("parameters");
        this.parameters = value;
    }

    public String getPassword() {
        checkSpecifiedProperty("password");

# Header Parameter Models

If you have a group of related **header parameters**, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

## Header Parameters with a Pydantic Model

            if openapi_examples:
                parameter["examples"] = jsonable_encoder(openapi_examples)
            elif example != Undefined:
                parameter["example"] = jsonable_encoder(example)
            if getattr(field_info, "deprecated", None):
                parameter["deprecated"] = True
            parameters.append(parameter)
    return parameters


def get_openapi_operation_request_body(
    *,

                // We rely on the fact that root is configured first
                "BuildEnvironmentService should be registered by the root"
            }
            parameters.rootProjectDir = this@with
            parameters.rootProjectBuildDir = project.layout.buildDirectory
        }
        val buildEnvironmentExtension = extensions.create("buildEnvironment", BuildEnvironmentExtension::class)

    interface Parameters : ValueSourceParameters {

        val ignoreIncomingBuildReceipt: Property<Boolean>

        @get:Optional
        val buildReceiptFileContents: Property<String>
    }

    override fun obtain(): String? = parameters.run {
        buildReceiptString()

def test_strings_in_generated_swagger():
    sig = inspect.signature(get_swagger_ui_html)
    swagger_js_url = sig.parameters.get("swagger_js_url").default  # type: ignore
    swagger_css_url = sig.parameters.get("swagger_css_url").default  # type: ignore
    swagger_favicon_url = sig.parameters.get("swagger_favicon_url").default  # type: ignore
    html = get_swagger_ui_html(openapi_url="/docs", title="title")

/// info

`Form` is a class that inherits directly from `Body`.

///

/// tip

To declare form bodies, you need to use `Form` explicitly, because without it the parameters would be interpreted as query parameters or body (JSON) parameters.

///

## About "Form Fields"

The way HTML forms (`<form></form>`) sends the data to the server normally uses a "special" encoding for that data, it's different from JSON.

import org.junit.runners.Parameterized.Parameters;

/** Tests for an undirected {@link StandardMutableGraph}. */
@AndroidIncompatible
@RunWith(Parameterized.class)
public class StandardMutableUndirectedGraphTest extends AbstractStandardUndirectedGraphTest {

  @Parameters(name = "allowsSelfLoops={0}, incidentEdgeOrder={1}")
  public static Collection<Object[]> parameters() {
    return Arrays.asList(
        new Object[][] {