title: Pysimplegui Combo dynamically refresh
body: <p>Good day everyone.
  Is there a way to dynamically add json values in the second Combo when the json element in the first Combo is selected?</p>
  <pre><code>import json
  import PySimpleGUI as sg
  
  
  file = {&quot;item 1&quot;: [{&quot;name&quot;: &quot;title 1&quot;}, {&quot;name&quot;: &quot;title 2&quot;}], &quot;item 2&quot;: [{&quot;name&quot;: &quot;title 3&quot;}, {&quot;name&quot;: &quot;title 4&quot;}]}
  j_file = json.dumps(file)
  
  layout = [[sg.Text('items'), sg.Combo(j_file, key='some_key', size=(30, 0))],  # there must be items
            [sg.Text('titles'), sg.Combo(j_file, key='other_key', size=(30, 0))]]  # there must be values of selected item
  window = sg.Window('testing', layout)
  while True:
      event, value = window.read()
      if event == sg.WINDOW_CLOSED:
          break
  </code></pre>