You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: pubkey_validity.rs
    path of file: ./repos/solana/zk-token-sdk/src/instruction
    
    the code of the file until where you have to start completion: //! The public-key validity proof instruction.
//!
//! A public-key validity proo
    
    pub fn new(keypair: &ElGamalKeypair) -> Result<Self, ProofGenerationError> {
        let pod_pubkey = pod::ElGamalPubkey(keypair.pubkey().to_bytes());

        let context = PubkeyValidityProofContext { pubkey: pod_pubkey };

        let mut transcript = context.new_transcript();
        let proof = PubkeyValidityProof::new(keypair, &mut transcript).into();

        Ok(PubkeyValidityData { context, proof })
    }