code: def format_filter_value(self, element, value):
          
          format_func = self.allowed_filter.get(element)
          return format_func(value)
docs: Calls the specific function to format value,
          depending on the given element.
  
          Arguments:
              element (string): The element of the VT to be formatted.
              value (dictionary): The element value.
  
          Returns:
              Returns a formatted value.