def METHOD_NAME(self, file_path, key_name, folder=None):
    """
    Upload a file to an s3 bucket.
    :param file_path: file to upload
    :param key_name: S3 key to create
    :param folder: S3 folder on which put the files (optional)
    """
    s3_folder = folder if folder else self.default_folder
    self.s3_client.upload_file(file_path, self.s3_bucket, s3_folder + key_name)