How to use the localstack.services.awslambda.lambda_api.ClientError function in localstack

return None
    if config.LAMBDA_FALLBACK_URL.startswith('dynamodb://'):
        table_name = urlparse(config.LAMBDA_FALLBACK_URL.replace('dynamodb://', 'http://')).netloc
        dynamodb = aws_stack.connect_to_service('dynamodb')
        item = {
            'id': {'S': short_uid()},
            'timestamp': {'N': str(now_utc())},
            'payload': {'S': str(data)}
        }
        aws_stack.create_dynamodb_table(table_name, partition_key='id')
        dynamodb.put_item(TableName=table_name, Item=item)
        return ''
    if re.match(r'^https?://.+', config.LAMBDA_FALLBACK_URL):
        response = safe_requests.post(config.LAMBDA_FALLBACK_URL, data)
        return response.content
    raise ClientError('Unexpected value for LAMBDA_FALLBACK_URL: %s' % config.LAMBDA_FALLBACK_URL)

with zipfile.ZipFile(BytesIO(zip_file_content)) as zip_ref:
            # TODO: check if this is still needed (probably not)
            jar_entries = [e for e in zip_ref.infolist() if e.filename.endswith('.jar')]
            if len(jar_entries) == 1:
                zip_file_content = zip_ref.read(jar_entries[0].filename)
                LOG.info('Found single jar file %s with %s bytes in Lambda zip archive' %
                         (jar_entries[0].filename, len(zip_file_content)))
                main_file = new_tmp_file()
                save_file(main_file, zip_file_content)
    if is_zip_file(zip_file_content):
        def execute(event, context):
            result, log_output = lambda_executors.EXECUTOR_LOCAL.execute_java_lambda(
                event, context, handler=handler, main_file=main_file)
            return result
        return execute, zip_file_content
    raise ClientError(error_response(
        'Unable to extract Java Lambda handler - file is not a valid zip/jar file', 400, error_type='ValidationError'))

def get_zip_bytes(function_code):
    """Returns the ZIP file contents from a FunctionCode dict.

    :type function_code: dict
    :param function_code: https://docs.aws.amazon.com/lambda/latest/dg/API_FunctionCode.html
    :returns: bytes of the Zip file.
    """
    if 'S3Bucket' in function_code:
        s3_client = aws_stack.connect_to_service('s3')
        bytes_io = BytesIO()
        try:
            s3_client.download_fileobj(function_code['S3Bucket'], function_code['S3Key'], bytes_io)
            zip_file_content = bytes_io.getvalue()
        except Exception as e:
            raise ClientError('Unable to fetch Lambda archive from S3: %s' % e, 404)
    elif 'ZipFile' in function_code:
        zip_file_content = function_code['ZipFile']
        zip_file_content = base64.b64decode(zip_file_content)
    else:
        raise ClientError('No valid Lambda archive specified.')
    return zip_file_content

:param function_code: https://docs.aws.amazon.com/lambda/latest/dg/API_FunctionCode.html
    :returns: bytes of the Zip file.
    """
    if 'S3Bucket' in function_code:
        s3_client = aws_stack.connect_to_service('s3')
        bytes_io = BytesIO()
        try:
            s3_client.download_fileobj(function_code['S3Bucket'], function_code['S3Key'], bytes_io)
            zip_file_content = bytes_io.getvalue()
        except Exception as e:
            raise ClientError('Unable to fetch Lambda archive from S3: %s' % e, 404)
    elif 'ZipFile' in function_code:
        zip_file_content = function_code['ZipFile']
        zip_file_content = base64.b64decode(zip_file_content)
    else:
        raise ClientError('No valid Lambda archive specified.')
    return zip_file_content

'Unable to find handler script (%s) in Lambda archive. %s' % (main_file, config_debug),
                    400, error_type='ValidationError'))

        if runtime.startswith('python') and not use_docker():
            try:
                # make sure the file is actually readable, then read contents
                ensure_readable(main_file)
                zip_file_content = load_file(main_file, mode='rb')
                # extract handler
                lambda_handler = exec_lambda_code(
                    zip_file_content,
                    handler_function=handler_function,
                    lambda_cwd=lambda_cwd,
                    lambda_env=lambda_environment)
            except Exception as e:
                raise ClientError('Unable to get handler function from lambda code.', e)

    add_function_mapping(lambda_name, lambda_handler, lambda_cwd)

    return {'FunctionName': lambda_name}