class RSpec::Core::SharedExampleGroupModule

def included(klass)

including example group.
Our definition evaluates the shared group block in the context of the
Ruby callback for when a module is included in another module is class. 
def included(klass)
  inclusion_line = klass.metadata[:location]
  SharedExampleGroupInclusionStackFrame.with_frame(@description, inclusion_line) do
    klass.class_exec(&@definition)
  end
end