title: Variable set using the set operator are not being propagated to the parent template in jinja
body: <p>parent.sql </p>
  
  <pre><code>I am in parent {{ itable }}
  </code></pre>
  
  <p>child.sql</p>
  
  <pre><code>{% extends 'test.sql' %}
  
  {% set itable = "test"  %}
  </code></pre>
  
  <p>When I run the my python code </p>
  
  <pre><code>template = env.get_template('child.sql')
      data = {
              'impressions_table': 'test'
          }
      j = jinjasql.JinjaSql(env=env)
      query, bind_params = j._prepare_query(
          template,
          data
      )
  </code></pre>
  
  <p>My output is</p>
  
  <pre><code>I am in test %s
  </code></pre>
  
  <p>This is a simple example for something complex I am doing I am looking for a way to propagate variable values up to parents.</p>
  
  <p>I have also tried using</p>
  
  <pre><code>include 
  </code></pre>
  
  <p>but I get an error saying expected end got with.</p>