How to use the nexusformat.nexus.tree.NXdata function in nexusformat

def scan_NXdata(self, scan):
        '''
        return the scan data in an NXdata object
        '''
        nxdata = NXdata()

        if len(scan.data) == 0:       # what if no data?
            # since no data available, provide trivial, fake data
            # this keeps the NXdata base class compliant with the NeXus standard
            nxdata.attrs['description'] = 'SPEC scan has no data'
            nxdata['noSpecData_y'] = NXfield([0, 0])   # primary Y axis
            nxdata['noSpecData_x'] = NXfield([0, 0])   # primary X axis
            nxdata.nxsignal = nxdata['noSpecData_y']
            nxdata.nxaxes   = [nxdata['noSpecData_x'], ]
            return nxdata

        nxdata.attrs['description'] = 'SPEC scan data'
        
        scan_type = scan.scanCmd.split()[0]
        if scan_type in ('mesh', 'hklmesh'):
            # hklmesh  H 1.9 2.1 100  K 1.9 2.1 100  -800000