import proveit
from proveit import n
from proveit.numbers import zero, one, two, Add
from proveit.numbers.numerals.decimals import two_def
from proveit.numbers.number_sets.natural_numbers import zero_in_nats, successor_in_nats
theory = proveit.Theory() # the theorem's theory
# testing
from proveit.numbers.numerals.decimals import tuple_len_2
%proving nat2
two_def
successor_in_nats
one_plus_one__in__nats = successor_in_nats.instantiate({n:one})
%qed