'Determine content type of the request body.
Does not do any body introspection, only checks header'

def get_content_type(self):

    if ('Content-Type' not in self.headers):
        return None
    content_type = self.content_type
    if ((not content_type) or (content_type == 'text/plain')):
        return None
    if (content_type not in get_supported_content_types()):
        raise exception.InvalidContentType(content_type=content_type)
    return content_type
