diff --git a/Lib/ipaddress.py b/Lib/ipaddress.py
@@ -376,8 +376,10 @@ def get_mixed_type_key(obj):
 
     """
     if isinstance(obj, _BaseNetwork):
+        obj = obj.ipv4_mapped or obj
         return obj._get_networks_key()
     elif isinstance(obj, _BaseAddress):
+        obj = obj.ipv4_mapped or obj
         return obj._get_address_key()
     return NotImplemented
 
@@ -423,6 +425,15 @@ def _check_int_address(self, address):
             raise AddressValueError(msg % (address, self._max_prefixlen,
                                            self._version))
 
+    @property
+    def ipv4_mapped(self):
+        """Returns an IPv4 address, maybe mapped by RFC 5156 from ::ffff:
+
+        Returns:
+            An IPv4Address instance or None
+        """
+        return None
+
     def _check_packed_address(self, address, expected_len):
         address_len = len(address)
         if address_len != expected_len:
@@ -668,6 +679,8 @@ def __hash__(self):
         return hash(int(self.network_address) ^ int(self.netmask))
 
     def __contains__(self, other):
+        if other._version == 6 and self._version == 4:
+            other = other.ipv4_mapped or other
         # always false if one is v4 and the other is v6.
         if self._version != other._version:
             return False
@@ -1916,6 +1929,19 @@ def __init__(self, address):
             raise AddressValueError("Unexpected '/' in %r" % address)
         self._ip = self._ip_int_from_string(addr_str)
 
+    @property
+    def ipv4_mapped(self):
+        """Return the IPv4 mapped address.
+
+        Returns:
+            If the IPv6 address is a v4 mapped address, return the
+            IPv4 mapped address. Return None otherwise.
+
+        """
+        if (self._ip >> 32) != 0xFFFF:
+            return None
+        return IPv4Address(self._ip & 0xFFFFFFFF)
+
     @property
     def packed(self):
         """The binary representation of this address."""
@@ -2012,19 +2038,6 @@ def is_loopback(self):
         """
         return self._ip == 1
 
-    @property
-    def ipv4_mapped(self):
-        """Return the IPv4 mapped address.
-
-        Returns:
-            If the IPv6 address is a v4 mapped address, return the
-            IPv4 mapped address. Return None otherwise.
-
-        """
-        if (self._ip >> 32) != 0xFFFF:
-            return None
-        return IPv4Address(self._ip & 0xFFFFFFFF)
-
     @property
     def teredo(self):
         """Tuple of embedded teredo IPs.

diff --git a/Lib/test/test_ipaddress.py b/Lib/test/test_ipaddress.py
@@ -583,7 +583,10 @@ class ComparisonTests(unittest.TestCase):
     v6net = ipaddress.IPv6Network(1)
     v6intf = ipaddress.IPv6Interface(1)
 
-    v4_addresses = [v4addr, v4intf]
+    v4mapaddr = ipaddress.IPv6Address('::ffff:0:1')
+    v4mapnet = ipaddress.IPv6Address('::ffff:0:1')
+
+    v4_addresses = [v4addr, v4intf, v4mapaddr]
     v4_objects = v4_addresses + [v4net]
     v6_addresses = [v6addr, v6intf]
     v6_objects = v6_addresses + [v6net]
@@ -684,7 +687,7 @@ def test_foreign_type_ordering(self):
 
     def test_mixed_type_key(self):
         # with get_mixed_type_key, you can sort addresses and network.
-        v4_ordered = [self.v4addr, self.v4net, self.v4intf]
+        v4_ordered = [self.v4addr, self.v4mapaddr, self.v4net, self.v4intf]
         v6_ordered = [self.v6addr, self.v6net, self.v6intf]
         self.assertEqual(v4_ordered,
                          sorted(self.v4_objects,

diff --git a/Lib/test/test_minidom.py b/Lib/test/test_minidom.py
@@ -2,6 +2,7 @@
 
 import copy
 import pickle
+from io import StringIO
 from test.support import findfile
 import unittest
 
@@ -188,6 +189,14 @@ def testReplaceChildFragment(self):
         frag.unlink()
         dom.unlink()
 
+    def testWriteXMLChildFragment(self):
+        dom, orig, c1, c2, c3, frag = self._create_fragment_test_nodes()
+        written = StringIO()
+        frag.writexml(writer=written, indent=' ', addindent='-', newl=':')
+        self.assertEquals(written.getvalue(), ' foo: bar: bat:')
+        frag.unlink()
+        dom.unlink()
+
     def testLegalChildren(self):
         dom = Document()
         elem = dom.createElement('element')
@@ -235,8 +244,10 @@ def testNonZero(self):
 
     def testUnlink(self):
         dom = parse(tstfile)
+        self.confirm(isinstance(dom, Document))
         self.assertTrue(dom.childNodes)
         dom.unlink()
+        self.confirm(isinstance(dom, Document))
         self.assertFalse(dom.childNodes)
 
     def testContext(self):

diff --git a/Lib/xml/dom/minidom.py b/Lib/xml/dom/minidom.py
@@ -340,6 +340,9 @@ class DocumentFragment(Node):
     def __init__(self):
         self.childNodes = NodeList()
 
+    def writexml(self, writer, indent="", addindent="", newl=""):
+        for node in self.childNodes:
+            node.writexml(writer, indent, addindent, newl)
 
 class Attr(Node):
     __slots__=('_name', '_value', 'namespaceURI',