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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 url(context, view, subdomain=UNSET, *args, **kwargs):
 """ Resolves a URL in a template, using subdomain-based URL resolution. If no subdomain is provided and a ``request`` is in the template context when rendering, the URL will be resolved relative to the current request's subdomain. If no ``request`` is provided, the URL will be resolved relative to current domain with the ``settings.ROOT_URLCONF``. Usage:: {% load subdomainurls %} {% url 'view-name' subdomain='subdomain' %} .. note:: This tag uses the variable URL syntax introduced in Django 1.3 as ``{% load url from future %}`` and was made the standard in Django 1.5. If you are upgrading a legacy application from one of the previous template tag formats, make sure to quote your constant string URL names to avoid :exc:`~django.core.urlresolver.NoReverseMatch` errors during template rendering. """

    if subdomain is UNSET:
        request = context.get('request')
        if request is not None:
            subdomain = getattr(request, 'subdomain', None)
        else:
            subdomain = None
    elif subdomain is '':
        subdomain = None

    return reverse(view, subdomain=subdomain, args=args, kwargs=kwargs)