How to use the instana.singletons.tracer function in instana

def gen_opentracing():
    with tracer.start_active_span('asteroid') as pscope:
        pscope.span.set_tag(ext.COMPONENT, "Python simple example app")
        pscope.span.set_tag(ext.SPAN_KIND, ext.SPAN_KIND_RPC_SERVER)
        pscope.span.set_tag(ext.PEER_HOSTNAME, "localhost")
        pscope.span.set_tag(ext.HTTP_URL, "/python/simple/one")
        pscope.span.set_tag(ext.HTTP_METHOD, "GET")
        pscope.span.set_tag(ext.HTTP_STATUS_CODE, 200)
        pscope.span.log_kv({"foo": "bar"})

        with tracer.start_active_span('spacedust', child_of=pscope.span) as cscope:
            cscope.span.set_tag(ext.SPAN_KIND, ext.SPAN_KIND_RPC_CLIENT)
            cscope.span.set_tag(ext.PEER_HOSTNAME, "localhost")
            cscope.span.set_tag(ext.HTTP_URL, "/python/simple/two")
            cscope.span.set_tag(ext.HTTP_METHOD, "POST")
            cscope.span.set_tag(ext.HTTP_STATUS_CODE, 204)
            cscope.span.set_baggage_item("someBaggage", "someValue")

    return "<center><h1>🐍 Generated some OT spans... 🦄</h1></center>"

def setUp(self):
        """ Clear all spans before a test run """
        self.http = urllib3.PoolManager()
        self.recorder = tracer.recorder
        self.recorder.clear_spans()

def execute_command_with_instana(wrapped, instance, args, kwargs):
        parent_span = tracer.active_span

        # If we're not tracing, just return
        if parent_span is None or parent_span.operation_name in EXCLUDED_PARENT_SPANS:
            return wrapped(*args, **kwargs)

        with tracer.start_active_span("redis", child_of=parent_span) as scope:
            try:
                collect_tags(scope.span, instance, args, kwargs)
                if (len(args) > 0):
                    scope.span.set_tag("command", args[0])

                rv = wrapped(*args, **kwargs)
            except Exception as e:
                scope.span.log_exception(e)
                raise
            else:
                return rv

def task_prerun(*args, **kwargs):
        try:
            ctx = None
            task = kwargs.get('sender', None)
            task_id = kwargs.get('task_id', None)
            task = registry.tasks.get(task.name)

            headers = task.request.get('headers', {})
            if headers is not None:
                ctx = tracer.extract(opentracing.Format.HTTP_HEADERS, headers)

            scope = tracer.start_active_span("celery-worker", child_of=ctx)
            scope.span.set_tag("task", task.name)
            scope.span.set_tag("task_id", task_id)
            add_broker_tags(scope.span, task.app.conf['broker_url'])

            # Store the scope on the task to eventually close it out on the "after" signal
            task_catalog_push(task, task_id, scope, True)
        except:
            logger.debug("task_prerun: ", exc_info=True)