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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 make_router():
 """Return a WSGI application that searches requests to controllers """

    global router
    routings = [
        ('GET', '^/$', index),
        ('GET', '^/api/?$', index),
        ('POST', '^/api/1/calculate/?$', calculate.api1_calculate),
        ('GET', '^/api/2/entities/?$', entities.api2_entities),
        ('GET', '^/api/1/field/?$', field.api1_field),
        ('GET', '^/api/1/formula/(?P<name>[^/]+)/?$', formula.api1_formula),
        ('GET', '^/api/2/formula/(?:(?P<period>[A-Za-z0-9:-]*)/)?(?P<names>[A-Za-z0-9_+-]+)/?$', formula.api2_formula),
        ('GET', '^/api/1/parameters/?$', parameters.api1_parameters),
        ('GET', '^/api/1/reforms/?$', reforms.api1_reforms),
        ('POST', '^/api/1/simulate/?$', simulate.api1_simulate),
        ('GET', '^/api/1/swagger$', swagger.api1_swagger),
        ('GET', '^/api/1/variables/?$', variables.api1_variables),
        ]
    router = urls.make_router(*routings)
    return router