Error in running command "sim vehicle.py -w"

[sayakboi]

Traceback (most recent call last):
File "/home/omnizon/ardupilot/Tools/autotest/sim_vehicle.py", line 833, in
parser.add_option("-v", "--vehicle", type='choice', default=None, help="vehicle type (%s)" %(vehicle_options_string), choices=_options.keys())
File "/home/omnizon/anaconda3/lib/python3.7/optparse.py", line 1000, in add_option
option = self.option_class(*args, **kwargs)
File "/home/omnizon/anaconda3/lib/python3.7/optparse.py", line 581, in init
checker(self)
File "/home/omnizon/anaconda3/lib/python3.7/optparse.py", line 670, in _check_choice
% str(type(self.choices)).split("'")[1], self)
optparse.OptionError: option -v/--vehicle: choices must be a list of strings ('dict_keys' supplied)

I am getting the above error