code: def get_attribute_value(self, name, index):
          
          if index == MISSING:
              return
          elif self.attribute_types[name] in NUMERIC_TYPES:
              at = self.attribute_types[name]
              if at == TYPE_INTEGER:
                  return int(index)
              return Decimal(str(index))
          else:
              assert self.attribute_types[name] == TYPE_NOMINAL
              cls_index, cls_value = index.split(':')
              #return self.attribute_data[name][index-1]
              if cls_value != MISSING:
                  assert cls_value in self.attribute_data[name], \
                      'Predicted value "%s" but only values %s are allowed.' \
                          % (cls_value, ', '.join(self.attribute_data[name]))
              return cls_value
docs: Returns the value associated with the given value index
          of the attribute with the given name.
          
          This is only applicable for nominal and string types.