def is_derepFas(title):
    """
    Takes a fasta title line (with or without the initial '>'), and tests to see whether it looks
    like a usearch dereplicated title line - i.e., does it end "size=n;"?
    """
    title = title.strip(';')
    try:
        countclause = title.split(';')[-1] #try to split at ';'
        try:
            if countclause.split('=')[0]=='size': 
            #try to split at '='; and if it splits, is the first part "size"?
                derepped = True
            else:
                derepped = False
        except:
            derepped = False
    except:
        derepped = False
    return(derepped)