add legend

app.py

@@ -71,6 +71,11 @@ def molecule(input_pdb):
     allow-scripts allow-same-origin allow-popups 
     allow-top-navigation-by-user-activation allow-downloads" allowfullscreen="" 
     allowpaymentrequest="" frameborder="0" srcdoc='{x}'></iframe>
+    '<div style="position: absolute; top: 10px; right: 10px; background-color: white; padding: 10px; border: 1px solid black;">'
+    <table>'
+    '<tr><td style="background-color: #008000; width: 20px; height: 20px;"></td><td>Carbon (C)</td></tr>'
+    '</table>'
+    '</div>'
     <a href="data:application/octet-stream;base64,{base64_content}" download="structure.pdb">Download File</a>
     """