How do you handle Gemini API errors and implement robust error handling?

import time
from google import genai
from google.api_core import exceptions as google_exceptions

client = genai.Client()

def gemini_call_with_retry(prompt: str, model: str = "gemini-3.5-flash",
                           max_retries: int = 5) -> str:
    for attempt in range(max_retries):
        try:
            response = client.models.generate_content(
                model=model,
                contents=prompt,
            )
            # Check if blocked by safety filters:
            if not response.candidates:
                reason = response.prompt_feedback.block_reason
                raise ValueError(f"Response blocked: {reason}")

            return response.text

        except google_exceptions.ResourceExhausted:  # 429 rate limit
            wait = (2 ** attempt) + 0.1
            print(f"Rate limited. Waiting {wait:.1f}s...")
            time.sleep(wait)

        except google_exceptions.InvalidArgument as e:  # 400 bad request
            if "context window" in str(e).lower():
                raise ValueError("Prompt too long - reduce size.") from e
            raise  # Re-raise other bad request errors

        except google_exceptions.PermissionDenied:  # 403
            raise PermissionError("Invalid API key or insufficient permissions.")

        except google_exceptions.ServiceUnavailable:  # 503
            wait = 5 * (attempt + 1)
            print(f"Service unavailable. Waiting {wait}s...")
            time.sleep(wait)

        except google_exceptions.NotFound:  # 404
            raise ValueError(f"Model {model!r} not found or deprecated.")

    raise Exception(f"Max retries ({max_retries}) exceeded.")