no attribute 'WaveformSequence'

[simplehappy2600]

run dicom-ecg-plot 000.dcm abc.dcm

Traceback (most recent call last):
File "c:\Users\jiangyl\Anaconda3\Scripts\dicom-ecg-plot", line 62, in
minor_axis, interpretation)
File "c:\Users\jiangyl\Anaconda3\Scripts\dicom-ecg-plot", line 38, in convert
ecg = ECG(source)
File "F:\Users\jiangyl\Anaconda3\lib\site-packages\ecg\ecg.py", line 183, in init
sequence_item = self.dicom.WaveformSequence[0]
File "F:\Users\jiangyl\Anaconda3\lib\site-packages\pydicom\dataset.py", line 783, in getattr
return object.getattribute(self, name)
AttributeError: 'FileDataset' object has no attribute 'WaveformSequence'