Russell's letter to Frege in 1902 was after the first edition of the Formulario Mathematico but before the fifth one (1908). So I wondered if the discovery of Russell's paradox had made Peano to edit his formal system. In the Logica part I see no reference to Russell's paradox, only a reference to The principles of mathematics in the bibliography (p. 17).
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$\begingroup$ No because Peano did not produced an axiomatization of set theory. Peano discussed antinomies in his 1906 paper on Schroeder-Bernetsein: see English transaltion into Giuseppe Peano, Selected works (Hubert Kennedy editor), (1973). $\endgroup$– Mauro ALLEGRANZAMar 23 at 12:36