equals(otherModel) {
        // eslint-disable-next-line no-underscore-dangle
        return objectShallowEquals(this._fields, otherModel._fields);
    }
Returns a boolean indicating if `otherModel` equals this {@link Model} instance.
Equality is determined by shallow comparing their attributes.

This equality is used when you call {@link Model#update}.
You can prevent model updates by returning `true` here.
However, a model will always be updated if its relationships are changed.

@param  {Model} otherModel - a {@link Model} instance to compare
@return {Boolean} a boolean indicating if the {@link Model} instance's are equal.