def get_sharemap():
    """Return a dict mapping share identifier to list of IServer objects.
        This indicates which servers are holding which shares. For immutable
        files, the shareid is an integer (the share number, from 0 to N-1).
        For mutable files, it is a string of the form 'seq%d-%s-sh%d',
        containing the sequence number, the roothash, and the share number."""
