train: loop variable typing (mypy)

src/simurg/train/clusters.py

@@ -106,10 +106,10 @@ def fit_block(theta: F32, r: F32, use: npt.NDArray[np.bool_], haploid: npt.NDArr
     # a locus with a single cluster is homozygous: an AB-labelled lone cluster moves to AA or BB by position
     lone_ab = keep[:, 1] & ~keep[:, 0] & ~keep[:, 2]
     if lone_ab.any():
-        for i in np.flatnonzero(lone_ab).tolist():
+        for j in np.flatnonzero(lone_ab).tolist():
-            hom = 0 if m[i, 1] < 0.5 else 2
+            hom = 0 if m[j, 1] < 0.5 else 2
-            assign[i, assign[i] == 1] = hom
+            assign[j, assign[j] == 1] = hom
-            keep[i, 1], keep[i, hom] = False, True
+            keep[j, 1], keep[j, hom] = False, True
         counts = np.stack([(assign == k).sum(axis=1) for k in range(3)], axis=1)
     tm = np.full((L, 3), np.nan)
     td = np.full((L, 3), np.nan)