Objection.js issue

tags.model.js

const { BaseModel } = require('./_basemodel');

const Tags = class extends BaseModel {
    static get tableName() {
        return 'tags';
    }

   
    static get relationMappings() {
        const Users = new this.prototype.app.models.Users(this.prototype.app);
        const Notifications = new this.prototype.app.models.Notifications(
            this.prototype.app
        );
        const Links = new this.prototype.app.models.Links(this.prototype.app);

        return {
            user: {
                relation: Model.BelongsToOneRelation,
                modelClass: Users,
                join: {
                    from: 'users.id',
                    to: 'tags.user_id',
                },
            },

            notifications: {
                relation: Model.ManyToManyRelation,
                modelClass: Notifications,
                join: {
                    from: 'tags.id',
                    through: {
                        from: 'notification_tag.tag_id',
                        to: 'notification_tag.notification_id',
                    },
                    to: 'notifications.id',
                },
            },

            links: {
                relation: Model.ManyToManyRelation,
                modelClass: Links,
                join: {
                    from: 'tags.id',
                    through: {
                        from: 'link_tag.tag_id',
                        to: 'link_tag.link_id',
                    },
                    to: 'links.id',
                },
            },
        };
    }
};

module.exports = function (app) {
    Tags.prototype.app = app;
    return Tags;
};

user.model.js

// See https://vincit.github.io/objection.js/#models
// for more of what you can do here.
const { BaseModel } = require('./_basemodel');

const Users = class extends BaseModel {
  static get tableName() {
    return "users";
  }

  static get relationMappings() {
    const Cohorts = new this.prototype.app.models.Cohorts(this.prototype.app);
    const Tokens = new this.prototype.app.models.Tokens(this.prototype.app);
    const ProfileFields = new this.prototype.app.models.ProfileFields(
      this.prototype.app
    );

    return {
      cohort: {
        relation: Model.BelongsToOneRelation,
        modelClass: Cohorts,
        join: {
          from: "users.cohortId",
          to: "cohorts.id"
        }
      },
      tokens: {
        relation: Model.HasManyRelation,
        modelClass: Tokens,
        join: {
          from: "users.id",
          to: "tokens.userId"
        }
      },
      profileFields: {
        relation: Model.HasManyRelation,
        modelClass: ProfileFields,
        join: {
          from: "users.id",
          to: "profile_fields.userId"
        }
      }
    };
  }
};

module.exports = function(app) {
  Users.prototype.app = app;
  return Users;
};