Recursively evaluates a compiled expression using the specified context.
    Dict instances can contain a "__kwargs" key which will be used to update the
    dict with its content

def eval_expr(expr, context):
    """Recursively evaluates a compiled expression using the specified context.
    Dict instances can contain a "__kwargs" key which will be used to update the
    dict with its content
    """
    if isinstance(expr, list):
        rv = []
        for item in expr:
            rv.append(eval_expr(item, context))
        return rv
    if isinstance(expr, dict):
        rv = {}
        for k, v in expr.iteritems():
            rv[k] = eval_expr(v, context)
        kwargs = rv.pop("__kwargs", None)
        if kwargs:
            rv.update(kwargs)
        return rv
    if isinstance(expr, Expression):
        return expr.eval(context)
    return expr