def convert_case(self, key):
return key if self.use_default_casing else self.casing_function(key)<EOL>
Returns a key converted with this protocol casing method

        Converts case to send/read from the cloud

        When using Microsoft Graph API, the keywords of the API use
        lowerCamelCase Casing

        When using Office 365 API, the keywords of the API use PascalCase Casing

        Default case in this API is lowerCamelCase

        :param str key: a dictionary key to convert
        :return: key after case conversion
        :rtype: str