def is_GSEXDI(filename):
    line1 = open(filename, 'r').readline()
    return (line1.startswith('#XDI/1') and 'Epics StepScan File' in line1)
test if file is GSE XDI data file
dataset/ETHPy150Open xraypy/xraylarch/plugins/io/gse_xdiscan.py/is_GSEXDI