chore: apply ruff linting fixes to crews module

src/crewai/crews/crew_output.py

@@ -1,5 +1,5 @@
 import json
-from typing import Any, Dict, Optional
+from typing import Any
 
 from pydantic import BaseModel, Field
 
@@ -12,19 +12,21 @@ class CrewOutput(BaseModel):
     """Class that represents the result of a crew."""
 
     raw: str = Field(description="Raw output of crew", default="")
-    pydantic: Optional[BaseModel] = Field(
+    pydantic: BaseModel | None = Field(
         description="Pydantic output of Crew", default=None
     )
-    json_dict: Optional[Dict[str, Any]] = Field(
+    json_dict: dict[str, Any] | None = Field(
         description="JSON dict output of Crew", default=None
     )
     tasks_output: list[TaskOutput] = Field(
         description="Output of each task", default=[]
     )
-    token_usage: UsageMetrics = Field(description="Processed token summary", default={})
+    token_usage: UsageMetrics = Field(
+        description="Processed token summary", default_factory=UsageMetrics
+    )
 
     @property
-    def json(self) -> Optional[str]:
+    def json(self) -> str | None:  # type: ignore[override]
         if self.tasks_output[-1].output_format != OutputFormat.JSON:
             raise ValueError(
                 "No JSON output found in the final task. Please make sure to set the output_json property in the final task in your crew."
@@ -32,7 +34,7 @@ class CrewOutput(BaseModel):
 
         return json.dumps(self.json_dict)
 
-    def to_dict(self) -> Dict[str, Any]:
+    def to_dict(self) -> dict[str, Any]:
         """Convert json_output and pydantic_output to a dictionary."""
         output_dict = {}
         if self.json_dict:
@@ -44,10 +46,9 @@ class CrewOutput(BaseModel):
     def __getitem__(self, key):
         if self.pydantic and hasattr(self.pydantic, key):
             return getattr(self.pydantic, key)
-        elif self.json_dict and key in self.json_dict:
+        if self.json_dict and key in self.json_dict:
             return self.json_dict[key]
-        else:
-            raise KeyError(f"Key '{key}' not found in CrewOutput.")
+        raise KeyError(f"Key '{key}' not found in CrewOutput.")
 
     def __str__(self):
         if self.pydantic: