old_contents: const db = require('../db.js');
  
  module.exports = (self, offSet) => {
    const queryString = `SELECT UserLanguageLevel.User FROM UserLanguageLevel 
                           INNER JOIN LanguageLevel 
                             ON UserLanguageLevel.LanguageLevel = LanguageLevel.id
                           INNER JOIN Language
                             ON LanguageLevel.Language = Language.id
                           INNER JOIN Level
                             ON LanguageLevel.Level = Level.id
                           WHERE Language.name IN (${self.canTeach.map(language => language[0]).join(',')}) AND Level.name IN ('fluent', 'native')
                        `;
    // db.query();
  };
  
new_contents: const db = require('../db.js');
  
  module.exports = (self, offSet) => {
    const queryString = `(
                          SELECT users_languages_levels.user AS teach_id FROM users_languages_levels 
                           INNER JOIN languages_levels 
                             ON users_languages_levels.languages_levels = languages_levels.id
                           INNER JOIN languages
                             ON languages_levels.language = language.id
                           INNER JOIN levels
                             ON languages_levels.level = level.id
                           WHERE language.name IN (${self.canTeach.map(language => language[0]).join(',')}) AND level.name IN ('fluent', 'native')
                          ) AS teach
                          INNER JOIN
                          
                        `;
    // db.query();
  };
  
subject: Refactor to snakecase