``defined``
===========
``defined`` checks if a variable is defined in the current context. This is very
useful if you use the ``strict_variables`` option:
.. code-block:: jinja
{# defined works with variable names #}
{% if foo is defined %}
...
{% endif %}
{# and attributes on variables names #}
{% if foo.bar is defined %}
...
{% endif %}
{% if foo['bar'] is defined %}
...
{% endif %}
When using the ``defined`` test on an expression that uses variables in some
method calls, be sure that they are all defined first:
.. code-block:: jinja
{% if var is defined and foo.method(var) is defined %}
...
{% endif %}
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