Return a certificate object by giving the name in the apk file

def get_certificate(self, filename):
        """
            Return a certificate object by giving the name in the apk file
        """
        pkcs7message = self.get_file(filename)

        message, _ = decode(pkcs7message)
        cert = encode(message[1][3])
        # Remove the first identifier·
        # byte 0 == identifier, skip
        # byte 1 == length. If byte1 & 0x80 > 1, we have long format
        #                   The length of to read bytes is then coded
        #                   in byte1 & 0x7F
        cert = cert[2 + (cert[1] & 0x7F) if cert[1] & 0x80 > 1 else 2:]

        certificate = x509.load_der_x509_certificate(cert, default_backend())

        return certificate