def get_filter_histogram( filter_type = nil, search_string = nil)
      raise "no search string provieded!" if( search_string === nil)
      raise "invalid filter type" if( !self.filter_types.include?( filter_type))

      filterType = "filterType=" + filter_type.to_s
      fts = "fts=" + search_string.split().join( '+').to_s
      args  = [filterType, fts].join( '&')

      return call_api( __method__, args)
    end
def get_filter_histogram( filter_type = nil, search_string = nil)
      raise "no search string provieded!" if( search_string === nil)
      raise "invalid filter type" if( !self.filter_types.include?( filter_type))

      filterType = "filterType=" + filter_type.to_s
      fts = "fts=" + search_string.split().join( '+').to_s
      args  = [filterType, fts].join( '&')

      return call_api( __method__, args)
    end
This method returns a list of categories and product counts that describe the results
 of a given product query. The query is specified using the product query parameters.
 @param  [String]  filter_type
   The type of filter data to return. Possible values are
   Brand, Retailer, Price, Discount, Size and Color.
 @param  [String]  search_string The string to be in the query.
 @return [String]  A list of Category objects. Each Category has an id, name, and count
   of the number of query results in that category.