How should i use the TracerMiddleware in the readme？

[suparek]

import opentracing
from opentracing.scope_managers.tornado import TornadoScopeManager
from opentracing_instrumentation import span_in_stack_context, http_server


opentracing.tracer = MyOpenTracingTracer(scope_manager=TornadoScopeManager())


class TracerMiddleware(object):

    def __init__(self):
        # perform initialization similar to above, including installing
        # the client_hooks
        
    @gen.coroutine
    def __call__(self, request, handler, next_mw):
        request_wrapper = http_server.TornadoRequestWrapper(request=request)
        span = http_server.before_request(request=request_wrapper)

        @gen.coroutine
        def next_middleware_with_span():
            yield next_mw()

        yield run_coroutine_with_span(span=span,
                                      func=next_middleware_with_span)

        span.finish()


def run_coroutine_with_span(span, func, *args, **kwargs):
    """Wrap the execution of a Tornado coroutine func in a tracing span.

    This makes the span available through the get_current_span() function.

    :param span: The tracing span to expose.
    :param func: Co-routine to execute in the scope of tracing span.
    :param args: Positional args to func, if any.
    :param kwargs: Keyword args to func, if any.
    """
    with span_in_stack_context(span):
        return func(*args, **kwargs)