def _oauth_signature(consumer_token, method, url, parameters={}, token=None):
    parts = urlparse.urlparse(url)
    scheme, netloc, path = parts[:3]
    normalized_url = scheme.lower() + "://" + netloc.lower() + path

    base_elems = []
    base_elems.append(method.upper())
    base_elems.append(normalized_url)
    base_elems.append("&".join("%s=%s" % (k, _oauth_escape(str(v)))
                               for k, v in sorted(parameters.items())))
    base_string = "&".join(_oauth_escape(e) for e in base_elems)

    key_elems = [escape.utf8(consumer_token["secret"])]
    key_elems.append(escape.utf8(token["secret"] if token else ""))
    key = b"&".join(key_elems)

    hash = hmac.new(key, escape.utf8(base_string), hashlib.sha1)
    return binascii.b2a_base64(hash.digest())[:-1]
Creates a Freshbooks client for a freshbooks domain, using
dataset/ETHPy150Open D-L/SimpleBookMarks/src/tornado/auth.py/_oauth_signature--crossover with--dataset/ETHPy150Open freshbooks/refreshbooks/refreshbooks/api.py/AuthorizingClient