code: public static List<Authentication> getProxyAuthenticationsFrom(Assertion assertion) {
  		final List<Authentication> chain = assertion.getChainedAuthentications();
  		final List<Authentication> proxyAuthentications = chain.subList(0, chain.size()-1);
  		return proxyAuthentications;
  	}
docs: Extracts a list of proxy ${@link Authentication}s MINUS the original authenticated ${@link Principal} f
  from a provided ${@link Assertion} instance.
  <p/>
  It is a caller's of this method responsibility to ensure that provided ${@link Assertion} instance is not null
  to avoid NPE at runtime.
  
  @param assertion instance to retrieve a list of proxy ${@link Authentication}s from
  @return A list of proxy authentications
  @throws NullPointerException if provided Assertion is <i>null</i>