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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_cpus_by_arch(cls, arch):
 """ Get all CPUs info by arch Args: arch(str):
 CPU architecture Returns: lxml.etree.element: CPUs by arch XML Raises: :exc:`~LagoException`: If no such ARCH is found """


        with open('/usr/share/libvirt/cpu_map.xml', 'r') as cpu_map:
            cpu_xml = ET.parse(cpu_map)
        try:
            return cpu_xml.xpath('/cpus/arch[@name="{0}"]'.format(arch))[0]
        except IndexError:
            raise LagoException('No such arch: {0}'.format(arch))