code: public void removeTextSearchParameter(String key) {
  
          try {
              ParamType type = ParamType.valueOf(key);
              switch (type) {
                  case language:
                      m_searchObject.setLocale(getStartLocale());
                      break;
                  case text:
                      m_searchObject.setQuery(null);
                      break;
                  case expired:
                      m_searchObject.setIncludeExpired(false);
                      break;
                  case creation:
                      m_searchObject.setDateCreatedEnd(-1L);
                      m_searchObject.setDateCreatedStart(-1L);
                      break;
                  case modification:
                      m_searchObject.setDateModifiedEnd(-1L);
                      m_searchObject.setDateModifiedStart(-1L);
                      break;
                  default:
              }
              m_handler.onRemoveSearchParam(type);
              updateResultsTab(false);
              ValueChangeEvent.fire(this, m_searchObject);
          } catch (IllegalArgumentException e) {
              // should not happen
          }
      }
docs: Removes the given full text search criteria from the search object.<p>
  
  @param key the key of the parameter to remove