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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 get_os_version_codename(codename, version_map=OPENSTACK_CODENAMES):
    '''Determine OpenStack version number from codename.'''
    for k, v in six.iteritems(version_map):
        if v == codename:
            return k
    e = 'Could not derive OpenStack version for '\
        'codename: %s' % codename
    error_out(e)