Find and return a format by extension.

    :param extension: A string describing the extension of the format.

def find_by_extension(extension):
    """
    Find and return a format by extension.

    :param extension: A string describing the extension of the format.
    """
    for format in FORMATS:
        if extension in format.extensions:
            return format

    raise UnknownFormat('No format found with extension "%s"' % extension)