Function parse_p384_public_key 

fn parse_p384_public_key(public_key: &[u8]) -> Result<EcdsaPublicKey>

Extract the signer’s ECDSA P-384 public key from a supplied public key.

Accepts an X.509 certificate or a bare SubjectPublicKeyInfo, in PEM or DER form. The actual key parsing is delegated to the crypto crate.