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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def build(port=8000, fixtures=None):
 """ Builds a server file. 1. Extract mock response details from all valid docstrings in existing views 2. Parse and generate mock values 3. Create a store of all endpoints and data 4. Construct server file """

    extractor = Extractor()
    parser = Parser(extractor.url_details, fixtures)
    parser.parse()
    url_details = parser.results
    _store = get_store(url_details)
    store = json.dumps(_store)
    variables = str(Variable('let', 'store', store))
    functions = DATA_FINDER + GET_HANDLER + MODIFY_HANDLER + POST_HANDLER
    endpoints = []
    endpoint_uris = []
    for u in parser.results:
        endpoint = Endpoint()
        if u['method'].lower() in ['get', 'post']:
            method = u['method'].lower()
        else:
            method = 'modify'
        response = str(ResponseBody(method))

        # Check in store if the base url has individual instances
        u['url'], list_url = clean_url(u['full_url'], _store, u['method'].lower())
        if list_url is not None and u['method'].lower() == 'get':
            list_endpoint = Endpoint()
            list_endpoint.construct('get', list_url, response)
            if str(list_endpoint) not in endpoints:
                endpoints.append(str(list_endpoint))
            if list_endpoint.uri not in endpoint_uris:
                endpoint_uris.append(list_endpoint.uri)

        if method == 'modify':
            without_prefix = re.sub(r'\/(\w+)\_\_', '', u['url'])
            for k, v in _store.items():
                if without_prefix in k:
                    options = v.get('options', '{}')
                    options = ast.literal_eval(options)
                    modifiers = []
                    if options is not None:
                        modifiers = options.get('modifiers', [])
                    if modifiers:
                        for mod in modifiers:
                            if u['method'].lower() == mod:
                                mod_endpoint = Endpoint()
                                uri = without_prefix
                                if v.get('position') is not None and v['position'] == 'url':
                                    uri = re.sub(r'\/?\_\_key', '/:id', u['full_url'])
                                mod_endpoint.construct(u['method'].lower(), uri, response)
                                if str(mod_endpoint) not in endpoints:
                                    endpoints.append(str(mod_endpoint))
                                if mod_endpoint.uri not in endpoint_uris:
                                    endpoint_uris.append(mod_endpoint.uri)
        else:
            endpoint.construct(u['method'], u['url'], response)
            if str(endpoint) not in endpoints:
                endpoints.append(str(endpoint))
            if endpoint.uri not in endpoint_uris:
                endpoint_uris.append(endpoint.uri)

    endpoints = ''.join(endpoints)
    express = ExpressServer()
    express.construct(variables, functions, endpoints, port)
    return express