feat: add logging for None values and improve documentation

- Add logging for None token values
- Improve test documentation and structure
- Fix import sorting in tests

Part of #2198

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

src/crewai/agents/agent_builder/utilities/base_token_process.py

@@ -1,4 +1,8 @@
 from crewai.types.usage_metrics import UsageMetrics
+import logging
+
+
+logger = logging.getLogger(__name__)
 
 
 class TokenProcess:
@@ -27,10 +31,12 @@ class TokenProcess:
         Raises:
             ValueError: If tokens is negative.
         """
-        if tokens is not None:
+        if tokens is None:
-            if tokens < 0:
+            logger.debug("Received None value for token count")
-                raise ValueError("Token count cannot be negative")
+            return
-            self.cached_prompt_tokens += tokens
+        if tokens < 0:
+            raise ValueError("Token count cannot be negative")
+        self.cached_prompt_tokens += tokens
 
     def sum_successful_requests(self, requests: int) -> None:
         self.successful_requests += requests

tests/utilities/test_token_process.py

@@ -4,7 +4,10 @@ from crewai.agents.agent_builder.utilities.base_token_process import TokenProces
 
 
 class TestTokenProcess(unittest.TestCase):
+    """Test suite for TokenProcess class token counting functionality."""
+
     def setUp(self):
+        """Initialize a fresh TokenProcess instance before each test."""
         self.token_process = TokenProcess()
 
     def test_sum_cached_prompt_tokens_with_none(self):