'Verify and return the CDN-provided remote IP address.
For requests coming through the CDN, the value of REMOTE_ADDR will be
the IP address of one of the CDN\'s edge nodes rather than that of the
client itself.  The CDN can provide the remote client\'s true IP as well
as verification that the provided IP is indeed accurate via extra
headers, the details of which vary with each CDN.
This function should analyze the request environment and return the
remote client\'s true IP address if it\'s present and validates. If it is
not present or does not validate, it should return None.'

def get_client_ip(self, environ):

    raise NotImplementedError
