reconsider h = {} as PartFunc of X,Y by RELSET_1:12;
{h} is PartFunc-set of X,Y

proof

let x be Element of {h}; :: according to RFUNCT_3:def 3 :: thesis: x is PartFunc of X,Y
thus x is PartFunc of X,Y by TARSKI:def 1; :: thesis: verum

end;

hence not for b₁ being PartFunc-set of X,Y holds b₁ is empty ; :: thesis: verum