
  [;1m-spec inverse(Function1) -> Function2[0m
  [;1m                 when[0m
  [;1m                     Function1 :: a_function(),[0m
  [;1m                     Function2 :: a_function().[0m

  Returns the inverse of function [;;4mFunction1[0m.

    1> R1 = sofs:relation([{1,a},{2,b},{3,c}]),
    R2 = sofs:inverse(R1),
    sofs:to_external(R2).
    [{a,1},{b,2},{c,3}]
