Use def rather than lambda

Author: jlapeyre

qiskit/algorithms/time_evolvers/variational/solvers/var_qte_linear_solver.py

@@ -84,7 +84,7 @@ def lse_solver(self) -> Callable[[np.ndarray, np.ndarray], np.ndarray]:
     def lse_solver(self, lse_solver: Callable[[np.ndarray, np.ndarray], np.ndarray] | None) -> None:
         """Sets an LSE solver. Uses a ``np.linalg.lstsq`` callable if ``None`` provided."""
         if lse_solver is None:
-            lse_solver = lambda a, b: np.linalg.lstsq(a, b, rcond=1e-2)[0]
+            def lse_solver(a, b): return np.linalg.lstsq(a, b, rcond=1e-2)[0]
 
         self._lse_solver = lse_solver