code: def trace_integrations(integrations, tracer=None):
      
      integrated = []
  
      for item in integrations:
          module_name = 'opencensus.ext.{}.trace'.format(item)
          try:
              module = importlib.import_module(module_name)
              module.trace_integration(tracer=tracer)
              integrated.append(item)
          except Exception as e:
              log.warning('Failed to integrate module: {}'.format(module_name))
              log.warning('{}'.format(e))
  
      return integrated
docs: Enable tracing on the selected integrations.
      :type integrations: list
      :param integrations: The integrations to be traced.