[Feature Request] check method to check if key exist or not

[Rstar1998]

Is it possible to provide a method which checks if a key or keypath exists or not , like in the example shown below ?

var convict = require("convict");
var config = convict({
  env: {
    doc: 'The application environment.',
    format: String,
    default: 'development',
    env: 'NODE_ENV'
  },
  ip: {
    doc: 'The IP address to bind.',
    format: String,
    default: '127.0.0.1',
    env: 'IP_ADDRESS',
  },
  port: {
    doc: 'The port to bind.',
    format: 'int',
    default: 8080,
    env: 'PORT',
    arg: 'port'
  }
});

config.get('ports'); // gives me error since its not in schema 
/*
can we have something like this ?
if (config.checkpath('ports')){

}
else
{

}
*/