Enable tracing on the selected integrations.
    :type integrations: list
    :param integrations: The integrations to be traced.

def trace_integrations(integrations, tracer=None):
    """Enable tracing on the selected integrations.
    :type integrations: list
    :param integrations: The integrations to be traced.
    """
    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