Fix mypy errors in security/invariant directory

- Fix default_factory type in Event class
- Add missing type annotations to __rich_repr__ method
- Add missing type annotations to _Policy and _Monitor classes

openhands/security/invariant/client.py

@@ -50,7 +50,7 @@ def close_session(self) -> Union[None, Exception]:
         return None
 
     class _Policy:
-        def __init__(self, invariant):
+        def __init__(self, invariant: 'InvariantClient') -> None:
             self.server = invariant.server
             self.session_id = invariant.session_id
 
@@ -77,7 +77,7 @@ def get_template(self) -> tuple[str | None, Exception | None]:
             except (ConnectionError, Timeout, HTTPError) as err:
                 return None, err
 
-        def from_string(self, rule: str):
+        def from_string(self, rule: str) -> 'InvariantClient._Policy':
             policy_id, err = self._create_policy(rule)
             if err:
                 raise err
@@ -97,7 +97,7 @@ def analyze(self, trace: list[dict]) -> Union[Any, Exception]:
                 return None, err
 
     class _Monitor:
-        def __init__(self, invariant):
+        def __init__(self, invariant: 'InvariantClient') -> None:
             self.server = invariant.server
             self.session_id = invariant.session_id
             self.policy = ''
@@ -114,7 +114,7 @@ def _create_monitor(self, rule: str) -> tuple[str | None, Exception | None]:
             except (ConnectionError, Timeout, HTTPError) as err:
                 return None, err
 
-        def from_string(self, rule: str):
+        def from_string(self, rule: str) -> 'InvariantClient._Monitor':
             monitor_id, err = self._create_monitor(rule)
             if err:
                 raise err

openhands/security/invariant/nodes.py

@@ -1,3 +1,4 @@
+from typing import Any, Iterable, Tuple
 from pydantic import BaseModel, Field
 from pydantic.dataclasses import dataclass
 
@@ -10,7 +11,7 @@ class LLM:
 
 class Event(BaseModel):
     metadata: dict | None = Field(
-        default_factory=dict, description='Metadata associated with the event'
+        default_factory=lambda: dict(), description='Metadata associated with the event'
     )
 
 
@@ -30,7 +31,7 @@ class Message(Event):
     content: str | None
     tool_calls: list[ToolCall] | None = None
 
-    def __rich_repr__(self):
+    def __rich_repr__(self) -> Iterable[Any | tuple[Any] | tuple[str, Any] | tuple[str, Any, Any]]:
         # Print on separate line
         yield 'role', self.role
         yield 'content', self.content