search entrez using specified database
    and accession

def entrez(db, acc):
    """
    search entrez using specified database
    and accession
    """
    c1 = ['esearch', '-db', db, '-query', acc]
    c2 = ['efetch', '-db', 'BioSample', '-format', 'docsum']
    p1 = Popen(c1, stdout = PIPE, stderr = PIPE)
    p2 = Popen(c2, stdin = p1.stdout, stdout = PIPE, stderr = PIPE)
    return p2.communicate()