import proveit
from proveit import n
from proveit.numbers import zero, one, Add
from proveit.numbers.numerals.decimals import one_def
from proveit.numbers.number_sets.natural_numbers import zero_in_nats, successor_in_nats
theory = proveit.Theory() # the theorem's theory
%proving nat1
one_def
successor_in_nats
zero_plus_one__in__nats = successor_in_nats.instantiate({n:zero})
%qed