def prefix_indices(parts):
    """Find the indices for a name prefix ('von' part) in a list of tokens."""
    i, j = -1, -1

    for k, p in enumerate(parts):
        if p.value.islower() and p.type != 'braced':
            i = k
            break

    if i != -1:
        j = i + 1

        for k in range(i + 1, len(parts) - 1):
            if parts[k].value.islower() and parts[k].type != 'braced':
                j = k + 1

    return i, j if j < len(parts) else j - 1