问在将外部变量解码为结构时，不会为Vec<u8>实现parity_codec::codec::Input

EN

use hex::decode;
use hex_literal::hex;
use parity_codec::{Decode, Encode, Input};
use primitives::generic::UncheckedMortalExtrinsic;
use std::fmt;
use std::fmt::Debug;

fn main() {
    let extrinsic_hex: &'static str =  "81ffd43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d3c6b8941e2976034e67bdd1a999c3eff4403c8ceaf717f18d9760ab18573ab2ce870e9b751c2f14dd9883e54746e1eb6639978ceab49968c25176cc0d2507205040003000ca10f";
    let result = hex::decode(extrinsic_hex);
    match result {
        Ok(v1) => {
            let extr_option = UncheckedMortalExtrinsic::decode(&mut v1);
            ()
        }
        _ => {
            println!("Error decoding");
            ()
        }
    }
}

error: duplicate lang item in crate `sr_io`: `panic_impl`.
  |
  = note: first defined in crate `std`.

error: duplicate lang item in crate `sr_io`: `oom`.
  |
  = note: first defined in crate `std`.

error[E0277]: the trait bound `std::vec::Vec<u8>: parity_codec::codec::Input` is not satisfied
  --> core/decaddr/src/main.rs:13:20
   |
13 |             let extr_option=UncheckedMortalExtrinsic::decode(&mut v1);
   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `parity_codec::codec::Input` is not implemented for `std::vec::Vec<u8>`
   |
   = note: required by `parity_codec::codec::Decode::decode`