How to make modular helper in Sinatra

How to make modular helper in Sinatra

i want to make a method inside a module (for grouping reason) that can be
called as a module.method, something like this:
helpers do
module UserSession
def logged_in?
not session[:email].nil?
end
def logout!
session[:email] = nil
end
end
end
but when i try to call it using UserSession.logged_in? it said that
logged_in is not UserSession's method
undefined method `logged_in?' for UserSession:Module
when i move the method as UserSession's method:
helpers do
module UserSession
def self.logged_in?
not session[:email].nil? # error
end
def self.logout!
session[:email] = nil
end
end
end
it gives an error, that i could not access the session variable
undefined local variable or method `session' for UserSession:Module
what is the best solution for this problem?