Simlib for a specific field of view LSST OpSim

[anibal-art]

Hello, I want to create a SIMLIB file with a specific field from an LSST OpSim simulations.
I really don't find an example to do this and I really thank you the help for doing this.

The field on what I am interested is this.
`import numpy as np
coord1=np.asarray([269.3875, 269.3917, 270.7667, 269.3875]) #RA
coord2=np.asarray([-27.9944, -29.2208, -28.6108, -27.9944]) #Dec

def filt(ra,dec):
coord = []
if min(coord1)<ra<max(coord1):
coord.append(ra)
if min(coord2)<dec<max(coord2):
coord.append(dec)
else:
return False
return True, coord`

I know that I can use the entire OpSim database (the entire footprint) and then filter the fields on this area (either in the output of SNANA or in the SIMLIB) but it is slow. So I want to filter on the SIMLIB creation. How I can do this? Thank you for the help!