Improve typing and error checks in mask_mean

PiperOrigin-RevId: 923361640
Change-Id: I708b5b8888e826f24e1ed0f1aa73a48e8174a161

src/alphafold3/model/components/utils.py

@@ -11,6 +11,7 @@
 """Utility functions for training AlphaFold and similar models."""
 
 from collections import abc
+from collections.abc import Sequence
 import contextlib
 import numbers
 
@@ -19,7 +20,6 @@ import haiku as hk
 import jax.numpy as jnp
 import numpy as np
 
-
 VALID_DTYPES = [np.float32, np.float64, np.int8, np.int32, np.int64, bool]
 
 
@@ -48,23 +48,26 @@ def bfloat16_context():
     yield
 
 
-def mask_mean(mask, value, axis=None, keepdims=False, eps=1e-10):
+def mask_mean(
+    mask: jnp.ndarray,
+    value: jnp.ndarray,
+    axis: int | Sequence[int] | None = None,
+    keepdims: bool = False,
+    eps: float = 1e-10,
+) -> jnp.ndarray:
   """Masked mean."""
 
   mask_shape = mask.shape
   value_shape = value.shape
 
-  assert len(mask_shape) == len(
-      value_shape
-  ), 'Shapes are not compatible, shapes: {}, {}'.format(mask_shape, value_shape)
+  if len(mask_shape) != len(value_shape):
+    raise ValueError(f'Incompatible shapes: {mask_shape=}, {value_shape=}')
 
   if isinstance(axis, numbers.Integral):
     axis = [axis]
   elif axis is None:
     axis = list(range(len(mask_shape)))
-  assert isinstance(
-      axis, abc.Iterable
-  ), 'axis needs to be either an iterable, integer or "None"'
+  assert isinstance(axis, abc.Sequence)
 
   broadcast_factor = 1.0
   for axis_ in axis:
@@ -73,8 +76,8 @@ def mask_mean(mask, value, axis=None, keepdims=False, eps=1e-10):
     if mask_size == 1:
       broadcast_factor *= value_size
     else:
-      error = f'Shapes are not compatible, shapes: {mask_shape}, {value_shape}'
-      assert mask_size == value_size, error
+      if mask_size != value_size:
+        raise ValueError(f'Incompatible shapes: {mask_shape=}, {value_shape=}')
 
   return jnp.sum(mask * value, keepdims=keepdims, axis=axis) / (
       jnp.maximum(