code: @Deprecated
      public void setUserCustomVariable(String key, String value){
          if (value == null){
              removeCustomVariable(VISIT_CUSTOM_VARIABLE, key);
          } else {
              setCustomVariable(VISIT_CUSTOM_VARIABLE, new CustomVariable(key, value), null);
          }
      }
docs: Set a visit custom variable with the specified key and value at the first available index.
  All visit custom variables with this key will be overwritten or deleted
  @param key the key of the variable to set
  @param value the value of the variable to set at the specified key.  A null value will remove this parameter
  @deprecated Use the {@link #setVisitCustomVariable(CustomVariable, int)} method instead.