<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def export_public_key(vk, label):
 """ Export public key to text format. The resulting string can be written into a .pub file or appended to the ~/.ssh/authorized_keys file. """

    key_type, blob = serialize_verifying_key(vk)
    log.debug('fingerprint: %s', fingerprint(blob))
    b64 = base64.b64encode(blob).decode('ascii')
    return u'{} {} {}\n'.format(key_type.decode('ascii'), b64, label)