def filter_file_paths_by_extension(file_paths, ext='csv'):
    """
    Filters out file paths that do not have an appropriate extension.

    :param file_paths: list of file path strings
    :param ext: valid extension
    """
    valid_file_paths = []
    for file_path in file_paths:
        ext = ".%s" % ext if ext[0] != '.' else ext
        if not file_path.endswith(ext):
            continue
        valid_file_paths.append(file_path)
    return valid_file_paths