## Check the Virtual Environment is Active { #check-the-virtual-environment-is-active }

Check that the virtual environment is active (the previous command worked).

/// tip

This is **optional**, but it's a good way to **check** that everything is working as expected and you are using the virtual environment you intended.

///

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console
$ which python

      - name: standalone erasure
        run: |
          ${GITHUB_WORKSPACE}/.github/workflows/run-mint.sh "erasure" "minio" "minio123" "${{ steps.vars.outputs.sha_short }}"

      # FIXME: renable this back when we have a valid way to add deadlines for PUT()s (internode CreateFile)
      # - name: resiliency
      #   run: |
      #     ${GITHUB_WORKSPACE}/.github/workflows/run-mint.sh "resiliency" "minio" "minio123" "${{ steps.vars.outputs.sha_short }}"

It could look like this:

```plaintext
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/custompython/bin
```

This way, when you type `python` in the terminal, the system will find the Python program in `/opt/custompython/bin` (the last directory) and use that one.

////

//// tab | Windows

  public final boolean trySetAccessible() {
    // We can't call accessibleObject.trySetAccessible since that was added in Java 9 and this code
    // should work on Java 8. So we emulate it this way.
    try {
      accessibleObject.setAccessible(true);
      return true;
    } catch (Exception e) { // sneaky checked exception
      return false;
    }
  }

final class SingletonImmutableSet<E> extends ImmutableSet<E> {
  // We deliberately avoid caching the asList and hashCode here, to ensure that with
  // compressed oops, a SingletonImmutableSet packs all the way down to the optimal 16 bytes.

  final transient E element;

  SingletonImmutableSet(E element) {
    this.element = Preconditions.checkNotNull(element);
  }

  @Override
  public int size() {
    return 1;

# 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`.

When you mount a sub-application as described above, FastAPI will take care of communicating the mount path for the sub-application using a mechanism from the ASGI specification called a `root_path`.

That way, the sub-application will know to use that path prefix for the docs UI.

that developer, and the exec wrapper will fail to install the new app. To avoid that,
install another app with the same developer identity but with a different bundle id.
That way, the permission to install apps is held on to while the primary app is

<img src="/img/tutorial/path-params/image02.png">

The same way, there are many compatible tools. Including code generation tools for many languages.

## Pydantic { #pydantic }

	// since the `objectLayer==nil`  check is performed before any other checks inside the handlers.
	// The only aim is to generate an HTTP request in a way that the relevant/registered end point is evoked/called.

	nilBucket := "dummy-bucket"
	nilReq, err := newTestRequest(http.MethodGet, getBucketLocationURL("", nilBucket), 0, nil)
	if err != nil {