FromFCPartialFractionForm[exp] converts all FCPartialFractionForm symbols present in exp back into the standard representation.
Overview, ToFCPartialFractionForm, FCPartialFractionForm.
FromFCPartialFractionForm[FCPartialFractionForm[x, {}, x]]x
FromFCPartialFractionForm[FCPartialFractionForm[0, {{{x - 1, -2}, 1}}, x]]\frac{1}{(x-1)^2}
FromFCPartialFractionForm[FCPartialFractionForm[0, {{{x + 1, -1}, 1}, {{x - y, -2}, c}}, x]]\frac{c}{(x-y)^2}+\frac{1}{x+1}
FromFCPartialFractionForm[FCPartialFractionForm[0, {{{x + 1, -1}, 1}, {{x - y, -2}, c}}, x], Factoring -> Together]\frac{c x+c+x^2-2 x y+y^2}{(x+1) (x-y)^2}