code: public void put(String key, String value) {
          if (INVALID_CHRACTERTS.contains(key) || INVALID_CHRACTERTS.contains(value)) {
              LOG.error("Session key or value can not contain the following characters: spaces, |, & or :");
          }  else {
              this.changed = true;
              this.values.put(key, value);
          }
      }
docs: Adds a value to the session, overwriting an existing value
  
  @param key The key to store the value
  @param value The value to store