docs: def initialize(config):
          """Initialize method.
  
          :param config: current application config, injected
          :type config: Config
          """
          service_injection_config = config.get('SERVICE_INJECTION', ())
  
          if not isinstance(service_injection_config, (tuple, list)):
              service_injection_config = (service_injection_config,)
  
          for si_conf in service_injection_config:
              if isinstance(si_conf, str):
                  package_name, cls_name = si_conf.rsplit('.', 1)
                  ServiceInitializer._bind_service(package_name, cls_name)
              elif isinstance(si_conf, dict):
                  services = si_conf['list']
                  service_package = si_conf['package']
  
                  for cls_name in services:
                      module_name = camelcase_to_underscore(cls_name)
                      package_name = "{0}.{1}".format(service_package, module_name)
                      ServiceInitializer._bind_service(package_name, cls_name)