def as_channel(value):
    """Always return a channel name:

    .. code-block:: python

        >>> print(as_channel('chan'))
        #chan
        >>> print(as_channel('#chan'))
        #chan
        >>> print(as_channel('&chan'))
        &chan
    """
    if not value.startswith(('#', '&')):
        return '#' + value
    return value