diff --git a/github/GithubObject.UnitTest.py b/github/GithubObject.UnitTest.py
index 9841558d..05a503ed 100644
--- a/github/GithubObject.UnitTest.py
+++ b/github/GithubObject.UnitTest.py
@@ -28,6 +28,9 @@ class TestCaseWithGithubTestObject( unittest.TestCase ):
     def expectStatusPut( self, url ):
         return self.g.expect._statusRequest( "PUT", url )
 
+    def expectStatusGet( self, url ):
+        return self.g.expect._statusRequest( "GET", url )
+
     def expectDataPatch( self, url, data ):
         return self.g.expect._dataRequest( "PATCH", url, data )
 
@@ -214,7 +217,7 @@ class GithubObjectWithModifiableExtendedListAttribute( TestCaseWithGithubTestObj
         "GithubTestObject",
         BaseUrl( lambda obj: "/test" ),
         SimpleScalarAttributes( "a1", "a2" ),
-        ExtendedListAttribute( "a3s", ContainedObject, addable = True, removable = True )
+        ExtendedListAttribute( "a3s", ContainedObject, addable = True, removable = True, hasable = True )
     )
 
     def testAddToList( self ):
@@ -227,4 +230,11 @@ class GithubObjectWithModifiableExtendedListAttribute( TestCaseWithGithubTestObj
         self.expectStatusDelete( "/test/a3s/idRemove" ).andReturn( 204 )
         self.o.remove_from_a3s( a3ToRemove )
 
+    def testHasInList( self ):
+        a3ToQuery = self.ContainedObject( self.g.object, { "id": "idQuery", "name": "nameQuery" }, lazy = True )
+        self.expectStatusGet( "/test/a3s/idQuery" ).andReturn( 204 )
+        self.assertTrue( self.o.has_in_a3s( a3ToQuery ) )
+        self.expectStatusGet( "/test/a3s/idQuery" ).andReturn( 404 )
+        self.assertFalse( self.o.has_in_a3s( a3ToQuery ) )
+
 unittest.main()
diff --git a/github/GithubObject.py b/github/GithubObject.py
index 69db6e82..a57c3399 100644
--- a/github/GithubObject.py
+++ b/github/GithubObject.py
@@ -99,7 +99,29 @@ class ExtendedListAttribute:
         def updateAttributes( self, obj ):
             obj._updateAttributes( { self.__addName: ExtendedListAttribute.Adder( obj, self.__attributeName, self.__type ) } )
 
-    def __init__( self, attributeName, type, addable = False, removable = False ):
+    class Haser:
+        def __init__( self, obj, attributeName, type ):
+            self.__obj = obj
+            self.__attributeName = attributeName
+            self.__type = type
+
+        def __call__( self, toBeQueried ):
+            assert( isinstance( toBeQueried, self.__type ) )
+            return self.__obj._github._statusRequest( "GET", self.__obj._baseUrl + "/" + self.__attributeName + "/" + toBeQueried._identity ) == 204
+
+    class HasDefinition:
+        def __init__( self, attributeName, hasName, type ):
+            self.__hasName = hasName
+            self.__attributeName = attributeName
+            self.__type = type
+
+        def getValueFromRawValue( self, obj, rawValue ):
+            return rawValue
+
+        def updateAttributes( self, obj ):
+            obj._updateAttributes( { self.__hasName: ExtendedListAttribute.Haser( obj, self.__attributeName, self.__type ) } )
+
+    def __init__( self, attributeName, type, addable = False, removable = False, hasable = False ):
         self.__attributeName = attributeName
         self.__type = type
         self.__getName = "get_" + attributeName
@@ -111,6 +133,10 @@ class ExtendedListAttribute:
             self.__removeName = "remove_from_" + attributeName
         else:
             self.__removeName = None
+        if hasable:
+            self.__hasName = "has_in_" + attributeName
+        else:
+            self.__hasName = None
 
     def getAttributeDefinitions( self ):
         yield self.__getName, ExtendedListAttribute.GetDefinition( self.__attributeName, self.__getName, self.__type )
@@ -118,6 +144,8 @@ class ExtendedListAttribute:
             yield self.__addName, ExtendedListAttribute.AddDefinition( self.__attributeName, self.__addName, self.__type )
         if self.__removeName is not None:
             yield self.__removeName, ExtendedListAttribute.RemoveDefinition( self.__attributeName, self.__removeName, self.__type )
+        if self.__hasName is not None:
+            yield self.__hasName, ExtendedListAttribute.HasDefinition( self.__attributeName, self.__hasName, self.__type )
 
 class ExtendedScalarAttribute:
     class AttributeDefinition: