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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 is_valid_vpnv4_prefix(prefix):
 """Returns True if given prefix is a string represent vpnv4 prefix. Vpnv4 prefix is made up of RD:Ipv4, where RD is represents route distinguisher and Ipv4 represents valid dot-decimal ipv4 notation string. """

    if not isinstance(prefix, str):
        return False

    # Split the prefix into route distinguisher and IP
    tokens = prefix.split(':', 2)
    if len(tokens) != 3:
        return False

    # Validate route distinguisher
    if not is_valid_route_dist(':'.join([tokens[0], tokens[1]])):
        return False

    # Validate IPv4 prefix and return
    return is_valid_ipv4_prefix(tokens[2])