Specifically, it adds an address into the wallet.

Easy to test now thanks to https://github.com/bitcoin/bitcoin/pull/14410
```
diff --git a/test/functional/wallet_importmulti.py b/test/functional/wallet_importmulti.py
index 9ba6860..bff37b2 100755
--- a/test/functional/wallet_importmulti.py
+++ b/test/functional/wallet_importmulti.py
@@ -95,6 +95,7 @@ class ImportMultiTest(BitcoinTestFramework):
         assert_equal(address_assert['iswatchonly'], True)
         assert_equal(address_assert['ismine'], False)
         assert_equal(address_assert['timestamp'], timestamp)
+        assert_equal(address_assert['ischange'], True)
 
         # ScriptPubKey + internal + label
         self.log.info("Should not allow a label to be specified when internal is true")
```

bool fGood = true;
    {
        LOCK2(cs_main, pwallet->cs_wallet);
        EnsureWalletIsUnlocked(pwallet);
        fsbridge::ifstream file;
        file.open(request.params[0].get_str(), std::ios::in | std::ios::ate);
        if (!file.is_open()) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
        }
        nTimeBegin = chainActive.Tip()->GetBlockTime();
        int64_t nFilesize = std::max((int64_t)1, (int64_t)file.tellg());
        file.seekg(0, file.beg);
        
        
        uiInterface.ShowProgress(strprintf("%s " + _("Importing..."), pwallet->GetDisplayName()), 0, false); 
        while (file.good()) {
            uiInterface.ShowProgress("", std::max(1, std::min(99, (int)(((double)file.tellg() / (double)nFilesize) * 100))), false);
            std::string line;
            std::getline(file, line);
            if (line.empty() || line[0] == '#')
                continue;
            std::vector<std::string> vstr;
            boost::split(vstr, line, boost::is_any_of(" "));
            if (vstr.size() < 2)
                continue;
            CKey key = DecodeSecret(vstr[0]);
            if (key.IsValid()) {
                CPubKey pubkey = key.GetPubKey();
                assert(key.VerifyPubKey(pubkey));
                CKeyID keyid = pubkey.GetID();