import proveit
from proveit import A, B
from proveit.logic.booleans.implication import iff_def
from proveit.logic.booleans.conjunction import left_from_and
from proveit.logic.equality import rhs_via_equality
theory = proveit.Theory() # the theorem's theory
%proving iff_implies_right
iff_def
iff_def_spec = iff_def.instantiate({A:A, B:B})
iff_def_spec.derive_right_via_equality(
assumptions=iff_implies_right.conditions).derive_left()
%qed