In raspberry :why the function `getregs` in module `ptrace` not found in `ptrace`

backgroud

about raspberry pi :Linux raspberrypi 5.10.17-v7l+ #1421 SMP Thu May 27 14:00:13 BST 2021 armv7l GNU/Linux
cargo.toml:

[dependencies]
nix = "0.19.1"
libc = "0.2.68"
rustyline = "8.2.0"
gimli = { git = "https://github.com/gimli-rs/gimli", rev = "ad23cdb2", default-features = false, features = ["read"] }
object = { version = "0.25.3", default-features = false, features = ["read"] }
memmap = "0.7"
addr2line = "0.15.0"

problem

in function:

use nix::sys::ptrace;
--snip--
...
pub fn wait(&self, options: Option<WaitPidFlag>) -> Result<Status, nix::Error> {
        Ok(match waitpid(self.pid(), options)? {
            WaitStatus::Exited(_pid, exit_code) => Status::Exited(exit_code),
            WaitStatus::Signaled(_pid, signal, _core_dumped) => Status::Signaled(signal),
            WaitStatus::Stopped(_pid, signal) => {
                let regs = ptrace::**getregs**(self.pid())?;
                Status::Stopped(signal, regs.rip as usize)
            }
            other => panic!("waitpid returned unexpected status: {:?}", other),
        })
    }

have problem

cannot find function `getregs` in module `ptrace`
not found in `ptrace`

in ptrace ,the mod.rs

///! Provides helpers for making ptrace system calls 

#[cfg(any(target_os = "android", target_os = "linux"))]
mod linux;

#[cfg(any(target_os = "android", target_os = "linux"))]
pub use self::linux::*;

#[cfg(any(target_os = "dragonfly",
          target_os = "freebsd",
          target_os = "macos",
          target_os = "netbsd",
          target_os = "openbsd"))]
mod bsd;

#[cfg(any(target_os = "dragonfly",
          target_os = "freebsd",
          target_os = "macos",
          target_os = "netbsd",
          target_os = "openbsd"
          ))]
pub use self::bsd::*;

get into the linux mod ,found that in linux.rs ,the getregs existes

pub fn getregs(pid: Pid) -> Result<user_regs_struct> {
    ptrace_get_data::<user_regs_struct>(Request::PTRACE_GETREGS, pid)
}

I have tried to make the linux mod public in the ptrace mod,still got the problem