def _cdp_split_header_x_y_counts(header_split_count_1, header_split_count_2,
    refs):
    """
    For each header in reference that has > 0 alignments in 1 file
    
    dict --> {header: (split counts 1:split counts 2)}
    """
    counts_by_ref = {}
    for header in refs.headers():
        if header in header_split_count_1 and header in header_split_count_2:
            counts_by_ref[header] = header_split_count_1[header
                ], header_split_count_2[header]
        elif header in header_split_count_1 and header not in header_split_count_2:
            counts_by_ref[header] = header_split_count_1[header], 0
        elif header not in header_split_count_1 and header in header_split_count_2:
            counts_by_ref[header] = 0, header_split_count_2[header]
    return counts_by_ref
