new

# File activesupport/lib/active_support/notifications/fanout.rb, line 50
      def initialize
        @mutex = Mutex.new
        @string_subscribers = Concurrent::Map.new { |h, k| h.compute_if_absent(k) { [] } }
        @other_subscribers = []
        @all_listeners_for = Concurrent::Map.new
        @groups_for = Concurrent::Map.new
        @silenceable_groups_for = Concurrent::Map.new
      end