code: function isConflictError (err) {
      // return false if err is not an object
      if (typeof err !== 'object') {
          return false
      }
      // return false if error does not have mysql duplicate key code
      if (err.errno !== 1062) {
          return false
      }
      // return false if duplicate key error is not on parent id column
      if (err.message.indexOf(this.model.columnName('parentId')) === -1) {
          return false
      }
      // if all negative tests pass return true
      return true
  }
docs: @function isConflictError
  
  return true if argument is error from conflicting revision - i.e. a unique
  key constraint violation on the parentId column for the instance model
  
  @param {Error} err
  
  @returns {boolean}