$($Direction fields$)$ Write a python script to plot the direction field for the differential equation

dy

dx $$ ay $$ b$,$ in the following cases of a and b:

$($a$)$ Case $1$: a $0,$ b $0.$

$($b$)$ Case $2$: a $0,$ b $0.$

$($c$)$ Case $3$: a $0,$ b $0.$

$($d$)$ Case $4$: a $0,$ b $0.$

Provide the script for Case $1,$ and the plots for $($a$)-($d$).$