'Return the style_id (|str|) of the style of *style_type* matching
*style_or_name*. Returns |None| if the style resolves to the default
style for *style_type* or if *style_or_name* is itself |None|. Raises
if *style_or_name* is a style of the wrong type or names a style not
present in the document.'

def get_style_id(self, style_or_name, style_type):

    return self.styles.get_style_id(style_or_name, style_type)
