code: @Override
      public FastStringWriter append( final CharSequence csq )
      {
          if ( csq == null )
              write( "null" );
          else
              buf.append( csq );
          return this;
      }
docs: Appends the specified character sequence to this writer.
  
  <p>
  An invocation of this method of the form <tt>out.append(csq)</tt> behaves
  in exactly the same way as the invocation
  
  <pre>
  out.write( csq.toString() )
  </pre>
  
  <p>
  Depending on the specification of <tt>toString</tt> for the character
  sequence <tt>csq</tt>, the entire sequence may not be appended. For
  instance, invoking the <tt>toString</tt> method of a character buffer
  will return a subsequence whose content depends upon the buffer's
  position and limit.
  
  @param csq
  The character sequence to append. If <tt>csq</tt> is
  <tt>null</tt>, then the four characters <tt>"null"</tt> are
  appended to this writer.
  
  @return This writer
  
  @since 1.5