code: public Object inquireByOid(Oid oid)
  	throws GSSException {
  	if (oid == null) {
  	    throw new GlobusGSSException(GSSException.FAILURE,
  					 GlobusGSSException.BAD_ARGUMENT,
  					 "nullOption");
  	}
  
  	if (oid.equals(GSSConstants.X509_CERT_CHAIN)) {
  	    return (this.cred == null) ?
  		null :
  		this.cred.getCertificateChain();
  	}
  
  	return null;
      }
docs: Retrieves arbitrary data about this credential.
  Currently supported oid: <UL>
  <LI>
  {@link GSSConstants#X509_CERT_CHAIN GSSConstants.X509_CERT_CHAIN}
  returns certificate chain of this credential
  (<code>X509Certificate[]</code>).
  </LI>
  </UL>
  
  @param oid the oid of the information desired.
  @return the information desired. Might be null.
  @exception GSSException containing the following major error codes:
  <code>GSSException.FAILURE</code>