Reference:https://github.com/mitsuhiko/jinja2/issues/164

example:

    {% set the_var = 'foo' %}
    {% for e in elements %}
        {% set the_var = 'YES' %}
        the var: {{ the_var }}
    {%- endfor %}
    the_var: {{ the_var }}
Result:

  the_var: YES
  the_var: YES
  the_var: foo