diff --git a/swirl_dynamics/projects/debiasing/rectified_flow/data_utils.py b/swirl_dynamics/projects/debiasing/rectified_flow/data_utils.py
index b1930c8..fc32d9e 100644
--- a/swirl_dynamics/projects/debiasing/rectified_flow/data_utils.py
+++ b/swirl_dynamics/projects/debiasing/rectified_flow/data_utils.py
@@ -69,6 +69,35 @@
 _LENS2_STD_STATS_PATH = "/lzepedanunez/data/lens2/stats/lens2_std_stats_all_variables_240x121_lonlat_1961-2000.zarr"
 
 
+def maybe_expand_dims(
+    array: np.ndarray,
+    allowed_dims: tuple[int, ...],
+    trigger_expand_dims: int,
+    axis: int = -1,
+) -> np.ndarray:
+  """Expands the dimensions of a numpy array if necessary.
+
+  Args:
+    array: The numpy array to be possibly expanded.
+    allowed_dims: The dimensions that the array can have, raise an error
+      otherwise.
+    trigger_expand_dims: The dimension that triggers the expansion.
+    axis: The axis in which the extra dimension is added.
+
+  Returns:
+    The array possibly expanded if its dimension is trigger_expand_dims.
+  """
+  ndim = array.ndim
+  if ndim not in allowed_dims:
+    raise ValueError(
+        f"The array has {ndim} dimensions, but it should have one of the"
+        f" dimensions {allowed_dims}"
+    )
+  if ndim == trigger_expand_dims:
+    array = np.expand_dims(array, axis=axis)
+  return array
+
+
 class UnpairedDataLoader:
   """Unpaired dataloader for loading samples from two distributions."""