_relation(type, Target, options) {
        Target = resolveModel(Target);

        if (type !== 'morphTo' && !_.isFunction(Target)) {
          throw new Error(
            'A valid target model must be defined for the ' + _.result(this, 'tableName') + ' ' + type + ' relation'
          );
        }
        return new Relation(type, Target, options);
      }
Override this in your bookshelf instance to define a custom function that will resolve the location of a model or
collection when using the {@link Bookshelf#model} method or when passing a string with a model name in any of the
collection methods (e.g. {@link Model#hasOne}, {@link Model#hasMany}, etc.).

This will only be used if the specified name cannot be found in the registry. Note that this function
can return anything you'd like, so it's not restricted in functionality.

@example
const Customer = bookshelf.model('Customer', {
  tableName: 'customers'
})

bookshelf.resolve = (name) => {
  if (name === 'SpecialCustomer') return Customer;
}

@param {string} name The model name to resolve.
@return {*} The return value will depend on what your re-implementation of this function does.