code: function formatResponse (res) {
      // iterate over rows in response
      _.each(res, row => {
          // iterate over key/value pairs in row object
          _.each(row, (val, key) => {
              // convert nulls to undefined
              if (val === null) {
                  row[key] = undefined
              }
          })
      })
  }
docs: /* private functions 
  @function formatResponse
  
  perform formatting on db response data
  
  @param {array} res - database response data
  
  @returns {undefined}