def start(self, user, persist=False):
		self.user = user
		self.persist = persist
		if user is None:
			self.set_cookie( 'SID' )
			self.set_cookie( 'atime' )
			if self.cookies.has_key ( 'user' ):
				self.expire_cookie ( 'user' )
		else:
			self.cookies['user'] = user.nickname
			self.regen()
		## TODO: Cache-control
Calculate Hessian with complex-step derivative approximation
dataset/ETHPy150Open aht/suas/suas/session.py/CookieSession.start--crossover with--dataset/ETHPy150Open statsmodels/statsmodels/statsmodels/tools/numdiff.py/approx_hess_cs