# Body - Multiple Parameters

Now that we have seen how to use `Path` and `Query`, let's see more advanced uses of request body declarations.

## Mix `Path`, `Query` and body parameters

First, of course, you can mix `Path`, `Query` and request body parameter declarations freely and **FastAPI** will know what to do.

And you can also declare body parameters as optional, by setting the default to `None`:

=== "Python 3.10+"

// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Support for pidfd was added during the course of a few Linux releases:
//  v5.1: pidfd_send_signal syscall;
//  v5.2: CLONE_PIDFD flag for clone syscall;
//  v5.3: pidfd_open syscall, clone3 syscall;
//  v5.4: P_PIDFD idtype support for waitid syscall;
//  v5.6: pidfd_getfd syscall.

package os