human
Complete this python program:
def findReplace(col, nids, src, dst, regex=False, field=None, fold=True):
assistant
#Here is the Python program you requested.

    """Find and replace fields in a note.
    """
    mmap = {}
    if field:
        for m in col.models.all():
            for f in m['flds']:
                if (f['name'] == field):
                    mmap[str(m['id'])] = f['ord']
        if (not mmap):
            return 0
    if (not regex):
        src = re.escape(src)
    if fold:
        src = ('(?i)' + src)
    regex = re.compile(src)
    def repl(str):
        return re.sub(regex, dst, str)
    d = []
    snids = ids2str(nids)
    nids = []
    for (nid, mid, flds) in col.db.execute(('select    id,    mid,    flds    from    notes    where    id    in    ' + snids)):
        origFlds = flds
        sflds = splitFields(flds)
        if field:
            try:
                ord = mmap[str(mid)]
                sflds[ord] = repl(sflds[ord])
            except KeyError:
                continue
        else:
            for c in range(len(sflds)):
                sflds[c] = repl(sflds[c])
        flds = joinFields(sflds)
        if (flds != origFlds):
            nids.append(nid)
            d.append(dict(nid=nid, flds=flds, u=col.usn(), m=intTime()))
    if (not d):
        return 0
    col.db.executemany('update    notes    set    flds=:flds,mod=:m,usn=:u    where    id=:nid', d)
    col.updateFieldCache(nids)
    col.genCards(nids)
    return len(d)