About field output of strain in ABAQUS

Hi,

 

I am trying to extract the strain variable in abaqus and I use the following python command to set the field output request when setting up the model:
myModel.fieldOutputRequests['F-Output-1'].setValues(variables=('S', 'E', 'CSTRESS'))

I check the cae file and indeed see in the step module that the strain E is included in the F-Output-1. However, in the odb file, I can not see E in the variable list. The thing is if I add some other variables like displacement U, I can successfully see them in the odb file. I am wondering why for E it fails. Thanks!