Apply automatic linting fixes to src directory

Co-Authored-By: Joe Moura <joao@crewai.com>

src/crewai/knowledge/source/string_knowledge_source.py

@@ -1,4 +1,3 @@
-from typing import List, Optional
 
 from pydantic import Field
 
@@ -9,16 +8,17 @@ class StringKnowledgeSource(BaseKnowledgeSource):
     """A knowledge source that stores and queries plain text content using embeddings."""
 
     content: str = Field(...)
-    collection_name: Optional[str] = Field(default=None)
+    collection_name: str | None = Field(default=None)
 
-    def model_post_init(self, _):
+    def model_post_init(self, _) -> None:
         """Post-initialization method to validate content."""
         self.validate_content()
 
-    def validate_content(self):
+    def validate_content(self) -> None:
         """Validate string content."""
         if not isinstance(self.content, str):
-            raise ValueError("StringKnowledgeSource only accepts string content")
+            msg = "StringKnowledgeSource only accepts string content"
+            raise ValueError(msg)
 
     def add(self) -> None:
         """Add string content to the knowledge source, chunk it, compute embeddings, and save them."""
@@ -26,7 +26,7 @@ class StringKnowledgeSource(BaseKnowledgeSource):
         self.chunks.extend(new_chunks)
         self._save_documents()
 
-    def _chunk_text(self, text: str) -> List[str]:
+    def _chunk_text(self, text: str) -> list[str]:
         """Utility method to split text into chunks."""
         return [
             text[i : i + self.chunk_size]