def context
      c = Thread.current.thread_variable_get(NAME)
      if c.nil?
        c = Array.new
        Thread.current.thread_variable_set(NAME, c)
      end
      return c
    end
def context
      c = Thread.current.thread_variable_get(NAME)
      if c.nil?
        c = Array.new
        Thread.current.thread_variable_set(NAME, c)
      end
      return c
    end
Returns the Array acting as the storage stack for this
 NestedDiagnosticContext. A new storage Array is created for each Thread
 running in the application.