Defines the BaseFetcher abstract class with a priority-based fallback chain pattern. Each fetcher implements `fetch_*` methods and registers with a priority. The DataFetcherManager iterates through fetchers by priority, falling back on failure. This pattern is reusable for any multi-source data ingestion system where sources have different reliability and latency characteristics.

Provides a common interface for notification senders (WeChat, Feishu, Telegram, email, etc.). Each sender implements `send_to_*` methods with consistent error handling, chunking, and markdown stripping. The base pattern can be extracted to add new channels with minimal code, making it reusable for any multi-channel notification system.

Implements a tool registry pattern where each tool is defined as a ToolDefinition with parameters, policies (read-only/side-effect), and a handler. Tools are registered via decorators and can be discovered by the agent runtime. This pattern is reusable for building extensible agent tool systems with declarative policies.

Provides utility functions for sanitizing secrets (API keys, tokens) and URLs for safe logging and diagnostics. Uses regex patterns to redact sensitive information. This is a standalone, reusable module that can be dropped into any Python project needing secure logging.

A small utility function that combines clsx and tailwind-merge to merge Tailwind CSS class names without conflicts. This is a common pattern in React/Tailwind projects and is extracted as a reusable helper. It demonstrates clean separation of concerns and can be used in any Tailwind-based frontend.

Implements a cross-process file lock to prevent concurrent market review runs. Uses fcntl on Linux and a fallback for platforms without it. This pattern is reusable for any system that needs to deduplicate expensive operations across processes, such as scheduled tasks or cache refreshes.