<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def grok_vars(elements):
 """Returns a list of vars for which the value is being appropriately set This currently includes the default filter, for-based iterators, and the explicit use of set"""

    default_vars = []
    iterbody = None
    if hasattr(elements, 'body'):
        iterbody = elements.body
    elif hasattr(elements, 'nodes'):
        iterbody = elements.nodes

    for element in iterbody:
        if isinstance(element, jinja2.nodes.Output):
            default_vars = default_vars + grok_vars(element)
        elif isinstance(element, jinja2.nodes.Filter):
            e_name = grok_filter_name(element)
            if e_name not in default_vars:
                default_vars.append(e_name)
        elif isinstance(element, jinja2.nodes.For):
            default_vars = grok_for_node(element, default_vars)
        elif isinstance(element, jinja2.nodes.If):
            default_vars = grok_if_node(element, default_vars)
        elif isinstance(element, jinja2.nodes.Assign):
            default_vars.append(element.target.name)
        elif isinstance(element, jinja2.nodes.FromImport):
            for from_var in element.names:
                default_vars.append(from_var)

    return default_vars