Downloads and saves public key(s).

    Downloads public key(s) from the TVM service for a given client id and saves in the storage
    for further usage.
    Note, that the cocaine-runtime automatically refreshes its keyring after this call.

def keyring_update(cid, **kwargs):
    """
    Downloads and saves public key(s).

    Downloads public key(s) from the TVM service for a given client id and saves in the storage
    for further usage.
    Note, that the cocaine-runtime automatically refreshes its keyring after this call.
    """
    ctx = Context(**kwargs)
    ctx.execute_action('keyring:update', **{
        'tvm': ctx.repo.create_secure_service('tvm'),
        'cid': cid,
    })