Check that a given HAL id is a valid one.

    :param hal_id: The HAL id to be checked.
    :returns: Boolean indicating whether the HAL id is valid or not.

    >>> is_valid("hal-01258754, version 1")
    True

    >>> is_valid("hal-01258754")
    True

    >>> is_valid("hal-01258754v2")
    True

    >>> is_valid("foobar")
    False

def is_valid(hal_id):
    """
    Check that a given HAL id is a valid one.

    :param hal_id: The HAL id to be checked.
    :returns: Boolean indicating whether the HAL id is valid or not.

    >>> is_valid("hal-01258754, version 1")
    True

    >>> is_valid("hal-01258754")
    True

    >>> is_valid("hal-01258754v2")
    True

    >>> is_valid("foobar")
    False
    """
    match = REGEX.match(hal_id)
    return (match is not None) and (match.group(0) == hal_id)