You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: abstract_executor_service.rb
    path of file: ./repos/brew/Library/Homebrew/vendor/bundle-standalone/ruby/2.3.0/gems/concurrent-ruby-1.1.4/lib/concurrent/executor
    
    the code of the file until where you have to start completion: require 'concurrent/errors'
require 'concurrent/executor/executor_service'
r
    
    def handle_fallback(*args)
      case fallback_policy
      when :abort
        raise RejectedExecutionError
      when :discard
        false
      when :caller_runs
        begin
          yield(*args)
        rescue => ex
          # let it fail
          log DEBUG, ex
        end