def create_variant_to_alt_read_names_dict(isovar_results):
    """
    Create dictionary from variant to names of alt reads supporting
    that variant in an IsovarResult.

    Parameters
    ----------
    isovar_results : list of IsovarResult

    Returns
    -------
    Dictionary from varcode.Variant to set(str) of read names

    """
    return {
        isovar_result.variant: set(isovar_result.alt_read_names)
        for isovar_result in isovar_results
    }