docs: def WriteApprovalRequest(self, approval_request):
      """Writes an approval request object."""
      approvals = self.approvals_by_username.setdefault(
          approval_request.requestor_username, {})
  
      approval_id = str(os.urandom(16).encode("hex"))
      cloned_request = approval_request.Copy()
      cloned_request.timestamp = rdfvalue.RDFDatetime.Now()
      cloned_request.approval_id = approval_id
      approvals[approval_id] = cloned_request
  
      return approval_id