static findOrCreateBy(field, data, callback) {

    this.findBy(field, data[field], (err, model) => {

      if (err) {
        if (err.notFound) {
          return this.create(data, callback);
        } else {
          return callback(err);
        }
      } else {
        return callback(null, model);
      }

    });

  }
Finds a model with a provided field, value pair. Returns the first found.
@param {string} field Name of the field
@param {object} data Key-value pairs of Model creation data. Will use appropriate value to query for based on "field" parametere.
@param {function({Error} err, {Nodal.Model} model)} callback The callback to execute upon completion