public void add_MethodCall(CompilationUnit cu,Block node) throws CoreException, MalformedTreeException, BadLocationException 
	{		AST ast = node.getAST();
		ASTRewrite astRewrite= ASTRewrite.create(ast);

		SimpleName newName= ast.newSimpleName("call_m");
		MethodInvocation newInvocation = ast.newMethodInvocation();
		newInvocation.setName(newName);
		Statement newStatement = ast.newExpressionStatement(newInvocation);
		ListRewrite listRewrite = astRewrite.getListRewrite(node, Block.STATEMENTS_PROPERTY);
		
		listRewrite.insertFirst(newStatement,null);
		
//		doc = new Document(doc.get());  // class attribute doc denotes the current  working document
		doc = new Document(f_content); // class attribute f denotes the content of the current working document
		TextEdit edits = astRewrite.rewriteAST(doc,null);
		System.out.println("call_m is added BEFORE " + doc.get());
		
		edits.apply(doc);
		
		System.out.println("call_m is added AFTER " + doc.get());
}