def wf_link_id?(id)
      return true if id.is_a?(String) && id =~ /^\w{16}$/
      raise Wavefront::Exception::InvalidExternalLinkId
    end
def wf_link_id?(id)
      return true if id.is_a?(String) && id =~ /^\w{16}$/
      raise Wavefront::Exception::InvalidExternalLinkId
    end
Ensure the given argument is a valid external Link ID

 @param id [String] the external link ID to validate
 @return True if the link ID is valid
 @raise Wavefront::Exception::InvalidExternalLinkId if the
   link ID is not valid