'Allocate a named backend.'

@staticmethod
def allocate_backend(name, **kargs):

    try:
        return Backend.backends[name](**kargs)
    except KeyError:
        names = ',    '.join([("'%s'" % (_,)) for _ in Backend.backend_choices()])
        raise ValueError(('backend    must    be    one    of    (%s)' % (names,)))
