import re


def add_accessions2(genomes: dict) -> dict:
    """
    Some genomes have their assembly accession in the 'sourceName' field.

    Updates the the genome dict "assembly_accession" field for each genome found.
    """
    re_acc = re.compile(r"GC[AF]_\d{9}\.\d+")
    for name in genomes:
        hit = re_acc.search(genomes[name]["sourceName"])
        if hit:
            genomes[name]["assembly_accession"] = hit.group()
    return genomes