fix: miscellaneous online checker bug fixes

- consistency_relation: use .get() instead of direct key access in
  online_check to avoid KeyError when a variable lacks a tracked attribute
- contain_relation: use ASCII arrow in to_display_name for terminal safety
- collect_trace: demote InputOutputParam warning to debug to reduce noise

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Essoz

traincheck/collect_trace.py

@@ -104,7 +104,7 @@ def merge(a: dict, b: dict, path=[]):
                 func_instr_opts[func_name]["dump_args"] = True
                 func_instr_opts[func_name]["dump_ret"] = True
                 # TODO: convert the arguments to instr_opts_dict (currently not possible as the index indicates the index of the argument/ret value among other tensors not all arguments)
-                logger.warning(
+                logger.debug(
                     "Currently not supporting fine-grained dumping of arguments and return values for InputOutputParam"
                 )
 

traincheck/invariant/consistency_relation.py

@@ -626,7 +626,7 @@ def get_check_attr(param, varid):
                 for var2 in checker_data.type_map[ref_param.var_type]:
                     if var2 == varid:
                         continue
-                    if checker_data.varid_map[var2][ref_param.attr_name] is None:
+                    if checker_data.varid_map[var2].get(ref_param.attr_name) is None:
                         logger.debug(
                             f"Attribute {ref_param.attr_name} not found in variable {var2}"
                         )

traincheck/invariant/contain_relation.py

@@ -371,7 +371,7 @@ def _fmt_val(v: object) -> str:
                 return "non-zero" if v == "non_zero" else str(v)
 
             if pre is not _NOT_SET and post is not _NOT_SET:
-                return f"{parent_short}() changes {var_short}.{attr}: {_fmt_val(pre)} → {_fmt_val(post)}"
+                return f"{parent_short}() changes {var_short}.{attr}: {_fmt_val(pre)} --> {_fmt_val(post)}"
             if const is not _NOT_SET:
                 return f"{parent_short}() sees {var_short}.{attr} = {const}"
             return f"{parent_short}() accesses {var_short}.{attr}"