code: func (sc *SimpleCollection) AccessFilter() Filter {
  	return func(sd common.SignedData) bool {
  		if err := sc.accessPolicy.Evaluate([]*common.SignedData{&sd}); err != nil {
  			return false
  		}
  		return true
  	}
  }
docs: // AccessFilter returns the member filter function that evaluates signed data
  // against the member access policy of this collection