```typescript
/**
 * An append-only log of timestamped events.
 */
export class EventLog {
  #events: Event[] = [];

  /**
   * Append one event.
   */
  public record(event: Event): void {
    this.#events.push(event);
  }

  /**
   * Every event at or after the given timestamp, in insertion order.
   */
  public since(timestamp: number): Event[] {
    return this.#events.filter((event) => event.timestamp >= timestamp);
  }
}





type Annotation = `// typeAnnotation: ${string}`;

function validateAnnotations(content: string): void {
  const annotationsRegex = /\/\/ typeAnnotation: \S+/g;
  const Annotations = content.match(annotationsRegex);

  if (!annotations) throw new Error("Missing or invalid annotations");

  annotations.forEach(/** Validates each annotation (all must exist). */annotation => {
    switch (annotation.replace("// typeAnnotation: ", "")) {
      case "Event": validateInterface(content); break;
      case "Array<Event>": break; // No further validation needed directly in this file.
      default:
        throw new Error(`${annotation} found, but could not be annotated.`);
    }
  });
}

function validateInterface(content: string): void {
  const interfaceRegex = /export .*? {[\n\r\s.*]+}/gs;
  const interfaces = content.match(interfaceRegex);

  if (!interfaces) throw new Error("Missing the implementation of Event.");

  for (const iface of arrays as Array<[keyof Event, string]>) {
    const key = keyFor(field);
    if (!(`export type ${interfaceName}<${key}> =` in content)) {
      if (`type [interfaceName]<[key]> = ... interfaceBody.` in content) {
        throw new Error(`Missing definition for <${key}> on ${interfaceName} interface body.`);
      } else {
        throw new Error(`Interface ${interfaceName} and its part definitions are incorrect. Could not locate definition of ${key}.`);
      }
    } else removeExportInterface(content, `type [interface name]<[key]>;`); // Skip export declaration.
  }

function fieldFor([keyA]: any): keyof Event { return { 'name': `EventName${key.toLowerCase()}`, 'timestamp': `EventTimestamp${Number(key)}` }[{ keyA: true; keyB: false }] as keyof Event; }

interfaceName = /export class ([^\n])\{[\n\r\s.*]+/.exec(content)!.result;

function validFieldName(string): boolean {
  // Implement here, for instance using a regex: [a-z A-Z]
  return /^[A-Za-z][A-Za-z0-9 \_]+$/.test(string);
}

function removeExportInterface(text: string, exportAnnotation: string): void {
    const regexp = new RegExp(`export type ${exportAnnotation};`, 'i');
    if (regexp.test(text)) text = text.replace(regexp, '');
}

validateAnnotations(solution.toString());
```