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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 addr_info(addr):
 """ Interprets an address in standard tuple format to determine if it is valid, and, if so, which socket family it is. Returns the socket family. """


    # If it's a string, it's in the UNIX family
    if isinstance(addr, basestring):
        return socket.AF_UNIX

    # Verify that addr is a tuple
    if not isinstance(addr, collections.Sequence):
        raise ValueError("address is not a tuple")

    # Make sure it has at least 2 fields
    if len(addr) < 2:
        raise ValueError("cannot understand address")

    # Sanity-check the port number
    if not (0 <= addr[1] < 65536):
        raise ValueError("cannot understand port number")

    # OK, first field should be an IP address; suck it out...
    ipaddr = addr[0]

    # Empty string means IPv4
    if not ipaddr:
        if len(addr) != 2:
            raise ValueError("cannot understand address")

        return socket.AF_INET

    # See if it's valid...
    if netaddr.valid_ipv6(ipaddr):
        if len(addr) > 4:
            raise ValueError("cannot understand address")

        return socket.AF_INET6
    elif netaddr.valid_ipv4(ipaddr):
        if len(addr) != 2:
            raise ValueError("cannot understand address")

        return socket.AF_INET

    raise ValueError("cannot understand address")