function API(agent) {
  this.agent = agent
  this.shim = new TransactionShim(agent, 'NewRelicAPI')
  this.awsLambda = new AwsLambda(agent)
}
The exported New Relic API. This contains all of the functions meant to be
used by New Relic customers.

You do not need to directly instantiate this class, as an instance of this is
the return from `require('newrelic')`.

@param {object} agent Instantiation of lib/agent.js
@class