import proveit
# Prepare this notebook for defining the axioms of a theory:
%axioms_notebook # Keep this at the top following 'import proveit'.
from proveit import a, b, f, A, B, fa, fb
from proveit.logic import (And, Forall, Equals, NotEquals,
InSet, Functions, Injections)
%begin axioms
injective_def = Forall(
(A, B), Forall(
f,
Equals(InSet(f, Injections(A, B)),
And(InSet(f, Functions(A, B)),
Forall((a, b), NotEquals(fa, fb),
domain=A, condition=NotEquals(a, b))))
.with_wrap_after_operator()))
%end axioms