code: public Groundy arg(String key, CharSequence value) {
      mArgs.putCharSequence(key, value);
      return this;
    }
docs: Inserts a CharSequence value into the mapping of this Bundle, replacing any existing value for
  the given key.  Either key or value may be null.
  
  @param key a String, or null
  @param value a CharSequence, or null