title: Create custom ttk style same as 'clam' ttk Theme (button widget specific)
body: <p>I need to create a custom style for button widgets which has the same appearance as buttons using the ttk 'clam' theme.</p>
  
  <p>I can set the theme like:</p>
  
  <pre><code>s = ttk.Style()
  s.theme_use('clam')
  </code></pre>
  
  <p>However, given the nature of a theme, this will then set all ttk widgets to use 'clam'.</p>
  
  <p><strong>I would like to be able to set certain ttk buttons to use the clam appearance and others to use default ttk.</strong></p>
  
  <p>I have tried looking at the layouts and configurations of 'TButton' whilst the clam theme is in use but it seems that a theme is a collection of styles and I am unsure on how to 'map' a custom style based on the clam button style.</p>