langchain/tools/powerbi/tool.py/QueryPowerBITool/_check_cache
class QueryPowerBITool:    def _check_cache(self, tool_input: str) -> Optional[str]:
        """Check if the input is present in the cache.

        If the value is a bad request, overwrite with the escalated version,
        if not present return None."""
        if tool_input not in self.session_cache:
            return None
        return self.session_cache[tool_input]