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: configuration.rb
    path of file: ./repos/bugsnag-ruby/lib/bugsnag
    
    the code of the file until where you have to start completion: require "set"
require "socket"
require "logger"
require "bugsnag/middleware_stack"
require "bugsnag/middleware/callbacks"
require "bugsnag/middleware/discard_error_class"
require "bugsnag/middleware/exception_meta_data"
require "bugs
    
    def initialize
      @mutex = Mutex.new

      # Set up the defaults
      self.auto_notify = true
      self.send_environment = false
      self.send_code = true
      self.meta_data_filters = Set.new(DEFAULT_META_DATA_FILTERS)
      @redacted_keys = Set.new
      self.scopes_to_filter = DEFAULT_SCOPES_TO_FILTER
      self.hostname = default_hostname
      self.runtime_versions = {}
      self.runtime_versions["ruby"] = RUBY_VERSION
      self.runtime_versions["jruby"] = JRUBY_VERSION if defined?(JRUBY_VERSION)
      self.timeout = 15
      self.release_stage = ENV['BUGSNAG_RELEASE_STAGE']
      self.notify_release_stages = nil
      self.auto_capture_sessions = true

      # All valid breadcrumb types should be allowable initially
      self.enabled_automatic_breadcrumb_types = Bugsnag::Breadcrumbs::VALID_BREADCRUMB_TYPES.dup
      self.before_breadcrumb_callbacks = []
      @on_breadcrumb_callbacks = Breadcrumbs::OnBreadcrumbCallbackList.new(self)

      # Store max_breadcrumbs here instead of outputting breadcrumbs.max_items
      # to avoid infinite recursion when creating breadcrumb buffer
      @max_breadcrumbs = DEFAULT_MAX_BREADCRUMBS

      @endpoints = EndpointConfiguration.new(DEFAULT_NOTIFY_ENDPOINT, DEFAULT_SESSION_ENDPOINT)

      @enable_events = true
      @enable_sessions = true

      @metadata = {}
      @metadata_delegate = Utility::MetadataDelegate.new

      # SystemExit and SignalException are common Exception types seen with
      # successful exits and are not automatically reported to Bugsnag
      # TODO move these defaults into `discard_classes` when `ignore_classes`
      #      is removed
      self.ignore_classes = Set.new([SystemExit, SignalException])
      self.discard_classes = Set.new([])

      # Read the API key from the environment
      self.api_key = ENV["BUGSNAG_API_KEY"]

      # Read NET::HTTP proxy environment variables
      if (proxy_uri = ENV["https_proxy"] || ENV['http_proxy'])
        parse_proxy(proxy_uri)
      end