def METHOD_NAME(filename, formattername="CustomFormatter",
                             **options):
    """Load a formatter from a file.
    This method expects a file located relative to the current working
    directory, which contains a class named CustomFormatter. By default,
    it expects the Formatter to be named CustomFormatter; you can specify
    your own class name as the second argument to this function.
    Users should be very careful with the input, because this method
    is equivalent to running eval on the input file.
    Raises ClassNotFound if there are any problems importing the Formatter.
    .. versionadded:: 2.2
    """
    try:
        # This empty dict will contain the namespace for the exec'd file
        custom_namespace = {}
        with open(filename, 'rb') as f:
            exec(f.read(), custom_namespace)
        # Retrieve the class `formattername` from that namespace
        if formattername not in custom_namespace:
            raise ClassNotFound('no valid %s class found in %s' %
                                (formattername, filename))
        formatter_class = custom_namespace[formattername]
        # And finally instantiate it with the options
        return formatter_class(**options)
    except OSError as err:
        raise ClassNotFound('cannot read %s: %s' % (filename, err))
    except ClassNotFound:
        raise
    except Exception as err:
        raise ClassNotFound('error when loading custom formatter: %s' % err)