How to use the fullcalendar.EventSource.parse function in fullcalendar

static parse(rawInput, calendar) {
    let rawProps

    if (typeof rawInput === 'object') { // long form. might fail in applyManualStandardProps
      rawProps = rawInput
    } else if (typeof rawInput === 'string') { // short form
      rawProps = { url: rawInput } // url will be parsed with parseGoogleCalendarId
    }

    if (rawProps) {
      return EventSource.parse.call(this, rawProps, calendar)
    }

    return false
  }