code: function query(value, field, expression) {
      if (!expression) {
          return value;
      }
  
      var expressionQuery = {};
      expressionQuery[expression] = value;
      return expressionQuery;
  }
docs: Creates an object containing the expression key and value queried.
  
  @param {String} expression - This is the operator used in query.
  @param {String} field - This is the column being quried.
  @param {ObjectId|Number|Boolean} value - This is the value being quried.
  
  @returns {Object} expressionQuery - contains the expressions key and query value.