code: function lazyLoad (file, opts) {
    var fn = null
    return function _lazyLoad (params, options, callback) {
      if (fn === null) {
        fn = require(`./api/${file}.js`)(opts)
      }
      return fn(params, options, callback)
    }
  }
docs: It's unlikely that a user needs all of our APIs, and since require is a sync operation that takes time (given the amount of APIs we have), let's lazy load them, so a given API file will be required only if the user actually needs that API. The following implementation takes advantage of js closures to have a simple cache with the least overhead.