Error while post processing ERSSTv5

[premmom6]

from ninolearn.IO import read_raw
from ninolearn.preprocess.anomaly import postprocess
from ninolearn.preprocess.regrid import to2_5x2_5
sst_ERSSTv5 = read_raw.sst_ERSSTv5()
sst_ERSSTv5_regrid = to2_5x2_5(sst_ERSSTv5)
/home/psg/.conda/envs/ninolearn_xesmf/lib/python3.7/site-packages/xarray/core/dataarray.py:789: FutureWarning: elementwise comparison failed; returning scalar instead, but in the future will perform elementwise comparison
return key in self.data
postprocess(sst_ERSSTv5_regrid, new=True)
Process None from ERSSTv5

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Traceback (most recent call last):
File "", line 1, in
File "/home/psg/NINO/ninolearn-0.1/ninolearn/preprocess/anomaly.py", line 220, in postprocess
toProcessedDir(data, new)
File "/home/psg/NINO/ninolearn-0.1/ninolearn/preprocess/anomaly.py", line 148, in toProcessedDir
filename = generateFileName(data.name, dataset=data.dataset, suffix='nc')
File "/home/psg/NINO/ninolearn-0.1/ninolearn/utils.py", line 47, in generateFileName
filename = ','.join(filenamelist)
TypeError: sequence item 0: expected str instance, NoneType found