Using tastis for an ACQ

[SabujBera]

I have downloaded data from HST Legacy Archive(https://hla.stsci.edu/hlaview.html#Inventory|filterText%3D%24filterTypes%3D|query_string=CRL%20618&posfilename=&poslocalname=&posfilecount=&listdelimiter=whitespace&listformat=degrees&RA=70.723434&Dec=36.114834&Radius=0.001667&inst-control=all&inst=ACS&inst=ACSGrism&inst=WFC3&inst=WFPC2&inst=NICMOS&inst=NICGRISM&inst=COS&inst=WFPC2-PC&inst=STIS&inst=FOS&inst=GHRS&imagetype=best&prop_id=9430&spectral_elt=&proprietary=both&preview=1&output_size=256&cutout_size=12.8|ra=&dec=&sr=&level=&image=&inst=ACS%2CACSGrism%2CWFC3%2CWFPC2%2CNICMOS%2CNICGRISM%2CCOS%2CWFPC2-PC%2CSTIS%2CFOS%2CGHRS&ds=).

For an ACQ , I wanted to examine the flux of the brightest object using tastis by following the STIS DATA HANDBOOK using python.
But there showing an error that some types of keyword not found, in my case the keyword is 'BIASLEV'. But it should give the result if also the file not containing this keyword.
So please help with that.