getMapperByName (name) {
    return this._mappers[name]
  }
Return the mapper registered under the specified name.
Doesn't throw error if mapper doesn't exist.

@example <caption>Container#getMapperByName</caption>
// import { Container } from 'js-data';
const JSData = require('js-data');
const { Container } = JSData;
console.log('Using JSData v' + JSData.version.full);

const store = new Container();
// Container#defineMapper returns a direct reference to the newly created
// Mapper.
const UserMapper = store.defineMapper('user');
console.log(UserMapper === store.getMapper('user'));
console.log(UserMapper === store.as('user').getMapper());
console.log(store.getMapper('profile')); // Does NOT throw an error

@method Container#getMapperByName
@param {string} name {@link Mapper#name}.
@returns {Mapper}
@since 3.0.0