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: gpg.go
    path of file: ./repos/cds/sdk/gpg
    
    the code of the file until where you have to start completion: package gpg

import (
	"bytes"
	"fmt"
	"io"

	go_ed25519 "golang.org/x/crypto/ed25519"

	"github.com/keybase/go-crypto/ed25519"
	"github.com/keybase/go-crypto/openpgp"
	"github.com/keybase/go-crypto/openpgp/armor"
	"github.com/keybase/go-crypto/openpgp/packet"
	"github.com/pkg/errors"
)

type PrivateKey struct {
	*openpgp.Entity
}

func NewPrivateKeyFromPem(keyPem string, passphrase string) (*PrivateKey, error) {
	p, err := armor.Decode(bytes.Ne
    
func (k PublicKey) IsSignedBy(signerKey *PublicKey) *packet.Signature {
	for _, i := range k.Identities {
		for _, s := range i.Signatures {
			// Skip signature if IssuerKeyId doesn't match signer's key
			if s.IssuerKeyId != nil && *s.IssuerKeyId != signerKey.PrimaryKey.KeyId {
				continue
			}
			// Return true if signature s is valid
			if err := signerKey.PrimaryKey.VerifyUserIdSignature(i.Name, k.PrimaryKey, s); err == nil {
				return s
			}
		}
	}
	return nil
}