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: ecdsa_utils.go
    path of file: ./repos/apns2/vendor/github.com/golang-jwt/jwt/v4
    
    the code of the file until where you have to start completion: package jwt

import (
	"crypto/ecdsa"
	"crypto/x509"
	"encoding/pem"
	"errors"
)

var (
	ErrNotECPublicKey  = errors.New("key is not a valid ECDSA public key")
	ErrNotECPrivate
    
func ParseECPrivateKeyFromPEM(key []byte) (*ecdsa.PrivateKey, error) {
	var err error

	// Parse PEM block
	var block *pem.Block
	if block, _ = pem.Decode(key); block == nil {
		return nil, ErrKeyMustBePEMEncoded
	}

	// Parse the key
	var parsedKey interface{}
	if parsedKey, err = x509.ParseECPrivateKey(block.Bytes); err != nil {
		if parsedKey, err = x509.ParsePKCS8PrivateKey(block.Bytes); err != nil {
			return nil, err
		}
	}

	var pkey *ecdsa.PrivateKey
	var ok bool
	if pkey, ok = parsedKey.(*ecdsa.PrivateKey); !ok {
		return nil, ErrNotECPrivateKey
	}

	return pkey, nil
}