'Canonicalize the hypervisor type name
:param name: hypervisor type name to canonicalize
:returns: a canonical hypervisor type name'

@classmethod
def canonicalize(cls, name):

    if (name is None):
        return None
    newname = name.lower()
    if (newname == 'xapi'):
        newname = cls.XEN
    if (not cls.is_valid(newname)):
        raise exception.InvalidHypervisorVirtType(hv_type=name)
    return newname
