title: Converting tree list to hierarchy dict
body: <p>I have a list of elements with attrs:  parent, level, is_leaf_node, is_root_node, is_child_node.</p>
  
  <p>I want to convert this list to hierarchy dict.
  Example of output dict:</p>
  
  <pre><code>{
          'Technology':
              {
               'Gadgets':{},
               'Gaming':{},
               'Programming':
                  {
                      'Python':{},
                      'PHP':{},
                      'Ruby':{},
                      'C++':{}
                  },
               'Enterprise':{},
               'Mac':{},
               'Mobile':{},
               'Seo':{},
               'Ui':{},
               'Virtual Worlds':{},
               'Windows':{},
              },
          'News':{
              'Blogging':{},
              'Economics':{},
              'Journalism':{},
              'Politics':{},
              'News':{}
              },}
  </code></pre>
  
  <p>I don't know algorithm. How to do it? </p>