Returns `Content-Type` based on an array of content_types provided.

        :param content_types: List of content-types.
        :return: Content-Type (e.g. application/json).

def select_header_content_type(self, content_types):
        """
        Returns `Content-Type` based on an array of content_types provided.

        :param content_types: List of content-types.
        :return: Content-Type (e.g. application/json).
        """
        if not content_types:
            return 'application/json'

        content_types = [x.lower() for x in content_types]

        if 'application/json' in content_types or '*/*' in content_types:
            return 'application/json'
        else:
            return content_types[0]