fix: loco nginx config for 3d fields

apps/hiopy/loco.py

@@ -77,9 +77,16 @@ class LocoServer:
                                     cell_regex = "(0)"
                                 else:
                                     cell_regex = generator().numerical_range(*chunk_range)[1:-1]
-                            f.write(
-                                f'  "~^{v.name}/\\d+\\.\\d+\\.{cell_regex}$" ' f"loco_backend{r};\n"
-                            )
+                            if len(v.shape) == 3:
+                                f.write(
+                                    f'  "~^{v.name}/\\d+\\.\\d+\\.{cell_regex}$" ' f"loco_backend{r};\n"
+                                )
+                            elif len(v.shape) == 2:
+                                f.write(
+                                    f'  "~^{v.name}/\\d+\\.{cell_regex}$" ' f"loco_backend{r};\n"
+                                )
+                            else:
+                                raise RuntimeError(f"{len(v.shape)}-dimensional variables are not supported by loco.")
 
                 # use last rank for timestep assumption: this rank has
                 # the healpix order 0 grid where the information