code: public PdfStream getAsStream(PdfName key) {
          PdfStream stream = null;
          PdfObject orig = getDirectObject(key);
          if (orig != null && orig.isStream()) {
              stream = (PdfStream) orig;
          }
          return stream;
      }
docs: Returns a <CODE>PdfObject</CODE> as a <CODE>PdfStream</CODE>,
  resolving indirect references.
  
  The object associated with the <CODE>PdfName</CODE> given is retrieved
  and resolved to a direct object.
  If it is a <CODE>PdfStream</CODE>, it is cast down and returned as such.
  Otherwise <CODE>null</CODE> is returned.
  
  @param key A <CODE>PdfName</CODE>
  @return the associated <CODE>PdfStream</CODE> object,
  or <CODE>null</CODE>