strymread for relative_leadervel()

[erbaoxueCS]

hi, This is Junqing Zhang
here is another problem:

import strym
from strym import strymread
file= "2021-02-01-03-34-22_2T3W1RFVXLW102405_CAN_Messages.csv"
r =strymread(csvfile=file)
r.relative_leadervel()

when i use relative_leadervel() it return warning: dataframe empty. no message in dataframe.
it dose not show in every file. The file above is an example.