Notifme SDK is a Node.js library for sending transactional notifications across multiple channels (email, SMS, push, webpush, Slack, WhatsApp, voice). It provides a unified interface with a provider pattern, allowing users to configure one or more providers per channel with built-in multi-provider strategies (fallback, round-robin, no-fallback). The library handles authentication, request formatting, and error handling for each provider, and includes a development mode with a notification catcher for local testing. The architecture is centered around a Sender class that dispatches requests to channel-specific strategies, which in turn call provider instances. External dependencies include nodemailer, node-fetch, web-push, winston, and node-pushnotifications. The codebase uses Flow for type checking and Babel for transpilation, with comprehensive Jest tests achieving 100% coverage thresholds.