@staticmethod
def get_headers(request: dict, body_is_json: bool) ->dict:
    """
        Treat special value 'json' as Content-Type: application/json
        """
    predefined = {'json': {'Content-Type': 'application/json'}}
    if 'headers' in request and isinstance(request['headers'], str):
        for known in predefined:
            if request['headers'].lower() == known:
                return predefined[known]
    result = {}
    for name, val in request.get('headers', {}).items():
        for known in predefined:
            if name.lower() == known:
                result.update(predefined[known])
                break
        else:
            result.update({name: val})
    if body_is_json and 'Content-Type' not in result:
        result.update(predefined['json'])
    return result
