code: public void setConfig( String key, String value ) {
          if ( config == null ) {
              config = new HashMap<String, String>();
          }
          config.put( key, value );
      }
docs: Adds a single configuration options for the sessions created by this
  factory. Details on the supported options can be found in the source for
  {@link com.jcraft.jsch.Session#applyConfig()}.
  
  @param key
  The name of the option
  @param value
  The value of the option
  
  @see #setConfig(Map)
  @see com.jcraft.jsch.Session#setConfig(java.util.Hashtable)
  @see com.jcraft.jsch.Session#applyConfig()