this is the code scaffold for virus.py:

from $\_\_$future$\_\_$ import annotations

from abc import ABC, abstractmethod

from computer import Computer

from route import Route, RouteSeries

from branch$\_$decision import BranchDecision

class VirusType$($ABC$)$:

def $\_\_$init$\_\_($self$)->$ None:

self.computers $=[]$

def add$\_$computer$($self$,$ computer: Computer$)->$ None:

self.computers.append$($computer$)$

@abstractmethod

def select$\_$branch$($self$,$ top$\_$branch: Route, bottom$\_$branch: Route$)->$ BranchDecision:

raise NotImplementedError$()$

class TopVirus$($VirusType$)$:

def select$\_$branch$($self$,$ top$\_$branch: Route, bottom$\_$branch: Route$)->$ BranchDecision:

# Always select the top branch

return BranchDecision.TOP

class BottomVirus$($VirusType$)$:

def select$\_$branch$($self$,$ top$\_$branch: Route, bottom$\_$branch: Route$)->$ BranchDecision:

# Always select the bottom branch

return BranchDecision.BOTTOM

class LazyVirus$($VirusType$)$:

def select$\_$branch$($self$,$ top$\_$branch: Route, bottom$\_$branch: Route$)->$ BranchDecision:

$"""$

Try looking into the first computer on each branch,

take the path of the least difficulty.

$"""$

top$\_$route $=$ type$($top$\_$branch.store$)==$ RouteSeries

bot$\_$route $=$ type$($bottom$\_$branch.store$)==$ RouteSeries

if top$\_$route and bot$\_$route:

top$\_$comp $=$ top$\_$branch.store.computer

bot$\_$comp $=$ bottom$\_$branch.store.computer

if top$\_$comp.hacking$\_$difficulty $$ bot$\_$comp.hacking$\_$difficulty:

return BranchDecision.TOP

elif top$\_$comp.hacking$\_$difficulty $>$ bot$\_$comp.hacking$\_$difficulty:

return BranchDecision.BOTTOM

else:

return BranchDecision.STOP

# If one of them has a computer, don't take it$.$

# If neither do$,$ then take the top branch.

if top$\_$route:

return BranchDecision.BOTTOM

return BranchDecision.TOP

class RiskAverseVirus$($VirusType$)$:

def select$\_$branch$($self$,$ top$\_$branch: Route, bottom$\_$branch: Route$)->$ BranchDecision:

$"""$

This virus is risk averse and likes to choose the path with the lowest risk factor.

$"""$

raise NotImplementedError$()$

class FancyVirus$($VirusType$)$:

CALC$\_$STR $="73+8-2*2/"$

def select$\_$branch$($self$,$ top$\_$branch: Route, bottom$\_$branch: Route$)->$ BranchDecision:

$"""$

This virus has a fancy$-$pants and likes to overcomplicate its approach.

$"""$

raise NotImplementedError$()$