code: def format_value(column_dict, value, key=None):
      
      formatter = column_dict.get('formatter')
      prop = column_dict['__col__']
  
      res = value
  
      if value in ('', None,):
          res = ''
  
      elif formatter is not None:
          res = formatter(value)
  
      else:
          if hasattr(prop, "columns"):
              sqla_column = prop.columns[0]
              column_type = getattr(sqla_column.type, 'impl', sqla_column.type)
  
              formatter = FORMATTERS_REGISTRY.get_formatter(column_type, key)
              if formatter is not None:
                  res = formatter(value)
      return res
docs: Format a value coming from the database (for example converts datetimes to
      strings)
  
      :param column_dict: The column datas collected during inspection
      :param value: A value coming from the database
      :param key: The exportation key