def _json2coloring(coloring):
    """
    Convert all of the None entries in rowcol_map to full slices.

    Parameters
    ----------
    coloring : dict
        Dict of coloring metadata.

    Returns
    -------
    dict
        Dict of coloring metadata.
    """
    full_slice = slice(None)
    for mode in ('fwd', 'rev'):
        if mode in coloring:
            rcmap = coloring[mode][1]
            for i, entry in enumerate(rcmap):
                if entry is None:
                    rcmap[i] = full_slice

    return coloring