new

# File activesupport/lib/active_support/callbacks.rb, line 571
        def initialize(name, config)
          @name = name
          @config = {
            scope: [:kind],
            terminator: default_terminator
          }.merge!(config)
          @chain = []
          @all_callbacks = nil
          @single_callbacks = {}
          @mutex = Mutex.new
        end