def _get_names(_dict):
    """Recursively find the names in a serialized column dictionary.

    Parameters
    ----------
    _dict : `dict`
        Dictionary from astropy __serialized_columns__

    Returns
    -------
    all_names : `list` [`str`]
        All the column names mentioned in _dict and sub-dicts.
    """
    all_names = []
    for k, v in _dict.items():
        if isinstance(v, dict):
            all_names.extend(_get_names(v))
        elif k == 'name':
            all_names.append(v)
    return all_names