docs: improve error message for inconsistent type maps

Fix deepmodeling#4034.

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>

deepmd/utils/data_system.py

@@ -613,7 +613,11 @@ def _check_type_map_consistency(self, type_map_list):
                 min_len = min([len(ii), len(ret)])
                 for idx in range(min_len):
                     if ii[idx] != ret[idx]:
-                        raise RuntimeError(f"inconsistent type map: {ret!s} {ii!s}")
+                        raise RuntimeError(
+                            f"Inconsistent type map: {ret!s} {ii!s} in different data systems. "
+                            "If you didn't set model/type_map, please set it, "
+                            "since the type map of the model cannot be decided by data."
+                        )
                 if len(ii) > len(ret):
                     ret = ii
         return ret