What is the purpose of adding pyridine in these reactions (O.G. Backeberg and B. Staskun, J. Chem. Soc., 1962, 3961–3963),

where Raney Nickel is used as a catalyst for reducing nitriles to aldehydes in the presence of NaH2PO2 by using AcOH/H2O/pyridine as the solvent system?

Additionally, are there any suitable reagents that can replace pyridine in this reaction?

Until now, the majority of literature concerning the reaction involving Raney nickel and NaH2PO2 employs AcOH/H2O/pyridine as the solvent system.