title: Representation of all values in Flag enum
body: <p>I would like to have a "ALL" flag in my python Flags enum for which </p>
  
  <pre><code>myenum.EVERY_MEMBER &amp; myenum.ALL == myenum.EVERY_MEMBER
  </code></pre>
  
  <p>holds true. I currently have:</p>
  
  <pre><code>from enum import Flag, auto
  
  class RefreshFlags(Flag):
      NONE = 0
      EVENTS = auto()
      RESOURCES = auto()
      BUILDINGS = auto()
      DEFENSES = auto()
      .....
  </code></pre>
  
  <p>Because this enum might grow at any state of development I would like to have something like</p>
  
  <pre><code>@property
  def ALL(self):
      retval = self.NONE
      for member in self.__members__.values():
          retval |= member
      return retval
  </code></pre>
  
  <p>This does not work:</p>
  
  <pre><code>RefreshFlags.EVENTS  &amp; RefreshFlags.ALL
  
  TypeError: unsupported operand type(s) for &amp;: 'RefreshFlags' and 'property'
  </code></pre>
  
  <p>Please note that this question currently only relates to python 3.6 or later.</p>