'Arguments:
version (string): The data model version of the safe cookie
data that is checked for forward and backward
compatibility.
session_id (string): Unique and unguessable session
identifier to which this safe cookie data is bound.
key_salt (string): A securely generated random string that
is used to derive a usage-specific secret key for
signing the safe cookie data to protect against volume
attacks.
signature (string): Cryptographically created signature
for the safe cookie data that binds the session_id
and its corresponding user as described at the top of
this file.'

def __init__(self, version, session_id, key_salt, signature):

    self.version = version
    self.session_id = session_id
    self.key_salt = key_salt
    self.signature = signature
