'service_instance:
service client instance.
cert_file:
certificate file name/location. This is only used in hosted
service management.
protocol:
http or https.
request_session:
session object created with requests library (or compatible).
timeout:
timeout for the http request, in seconds.
user_agent:
user agent string to set in http header.'

def __init__(self, service_instance, cert_file=None, protocol='https', request_session=None, timeout=65, user_agent=''):

    self.service_instance = service_instance
    self.cert_file = cert_file
    self.protocol = protocol
    self.proxy_host = None
    self.proxy_port = None
    self.proxy_user = None
    self.proxy_password = None
    self.request_session = request_session
    self.timeout = timeout
    self.user_agent = user_agent
