code: function(model, logger) {
      // This line has to come first
      validationHelper.validateModel(model, logger)
  
      let readableFields = []
  
      let fields = model.schema.paths
  
      for (let fieldName in fields) {
        let field = fields[fieldName].options
        if (!field.exclude && fieldName !== '__v') {
          readableFields.push(fieldName)
        }
      }
  
      return readableFields
    }
docs: Get a list of fields that can be returned as part of a query result.
  @param model: A mongoose model object.
  @param logger: A logging object.
  @returns {Array}: A list of fields.