twee-2.5: tests/y-i.p

fof(k_def, axiom, ![X, Y]: (k @ X) @ Y = X).
fof(s_def, axiom, ![X, Y, Z]: ((s @ X) @ Y) @ Z = (X @ Z) @ (Y @ Z)).
fof(i_def, axiom, ![X]: i @ X = X).
fof(conjecture, conjecture, ?[Y]: ![F]: Y @ F = F @ (Y @ F)).