def set_shareholders(shareholders, servermap):
    """Tell the encoder where to put the encoded shares. 'shareholders'
        must be a dictionary that maps share number (an integer ranging from
        0 to n-1) to an instance that provides IStorageBucketWriter.
        'servermap' is a dictionary that maps share number (as defined above)
        to a set of peerids. This must be performed before start() can be
        called."""
