Sorts data by key using usual Python tuple sorting semantics
    or sorts in categorical order for any categorical Dimensions.

def dimension_sort(odict, kdims, vdims, key_index):
    """
    Sorts data by key using usual Python tuple sorting semantics
    or sorts in categorical order for any categorical Dimensions.
    """
    sortkws = {}
    ndims = len(kdims)
    dimensions = kdims+vdims
    indexes = [(dimensions[i], int(i not in range(ndims)),
                    i if i in range(ndims) else i-ndims)
                for i in key_index]
    cached_values = {d.name: [None]+list(d.values) for d in dimensions}

    if len(set(key_index)) != len(key_index):
        raise ValueError("Cannot sort on duplicated dimensions")
    else:
       sortkws['key'] = lambda x: tuple(cached_values[dim.name].index(x[t][d])
                                        if dim.values else x[t][d]
                                        for i, (dim, t, d) in enumerate(indexes))
    if sys.version_info.major == 3:
        return python2sort(odict.items(), **sortkws)
    else:
        return sorted(odict.items(), **sortkws)