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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def mac_address(value, allow_empty = False, **kwargs):
 """Validate that ``value`` is a valid MAC address. :param value: The value to validate. :type value: :class:`str <python:str>` / :obj:`None <python:None>` :param allow_empty: If ``True``, returns :obj:`None <python:None>` if ``value`` is empty. If ``False``, raises a :class:`EmptyValueError <validator_collection.errors.EmptyValueError>` if ``value`` is empty. Defaults to ``False``. :type allow_empty: :class:`bool <python:bool>` :returns: ``value`` / :obj:`None <python:None>` :rtype: :class:`str <python:str>` / :obj:`None <python:None>` :raises EmptyValueError: if ``value`` is empty and ``allow_empty`` is ``False`` :raises CannotCoerceError: if ``value`` is not a valid :class:`str <python:str>` or string-like object :raises InvalidMACAddressError: if ``value`` is not a valid MAC address or empty with ``allow_empty`` set to ``True`` """

    if not value and not allow_empty:
        raise errors.EmptyValueError('value (%s) was empty' % value)
    elif not value:
        return None

    if not isinstance(value, basestring):
        raise errors.CannotCoerceError('value must be a valid string, '
                                       'was %s' % type(value))

    if '-' in value:
        value = value.replace('-', ':')

    value = value.lower().strip()

    is_valid = MAC_ADDRESS_REGEX.match(value)

    if not is_valid:
        raise errors.InvalidMACAddressError('value (%s) is not a valid MAC '
                                            'address' % value)

    return value