Add 'mmap.flush'.

Author: fangerer

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/mmap/MMapBuiltins.java

@@ -517,7 +517,7 @@ protected static SequenceStorageNodes.AppendNode createAppend() {
         }
     }
 
-    @Builtin(name = "seek", fixedNumOfPositionalArgs = 1)
+    @Builtin(name = "seek", minNumOfPositionalArgs = 2, maxNumOfPositionalArgs = 3)
     @GenerateNodeFactory
     @TypeSystemReference(PythonArithmeticTypes.class)
     abstract static class SeekNode extends PythonBuiltinNode {
@@ -703,4 +703,15 @@ public static InternalLenNode create() {
         }
     }
 
+    @Builtin(name = "flush", fixedNumOfPositionalArgs = 1)
+    @GenerateNodeFactory
+    abstract static class FlushNode extends PythonUnaryBuiltinNode {
+
+        @Specialization
+        Object seek(@SuppressWarnings("unused") PMMap self) {
+            return PNone.NONE;
+        }
+
+    }
+
 }