module T::Helpers

def abstract! 

def abstract!
  Private::Abstract::Declare.declare_abstract(self, type: :abstract)
end

def final! 

def final!
  Private::Final.declare(self)
end

def interface! 

def interface!
  Private::Abstract::Declare.declare_abstract(self, type: :interface)
end

def mixes_in_class_methods(mod, *mods)

Except that it is statically analyzed by sorbet.

end
other.extend(mod)
def self.included(other)

Nearly equivalent to

Causes a mixin to also mix in class methods from the named module. 
def mixes_in_class_methods(mod, *mods)
  Private::Mixins.declare_mixes_in_class_methods(self, [mod].concat(mods))
end

def requires_ancestor(mod, *mods); end

TODO: implement the checks in sorbet-runtime.

end
include MyHelper
class MyClass < BasicObject # error: `MyClass` must include `Kernel` (required by `MyHelper`)

end
requires_ancestor Kernel

extend T::Helpers
module MyHelper

Example:

Specify an inclusion or inheritance requirement for `self`. 
def requires_ancestor(mod, *mods); end

def sealed! 

def sealed!
  Private::Sealed.declare(self, Kernel.caller(1..1)&.first&.split(':')&.first)
end