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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def extract_literal_bool(templatevar):
 """ See if a template FilterExpression holds a literal boolean value. :type templatevar: django.template.FilterExpression :rtype: bool|None """

    # FilterExpression contains another 'var' that either contains a Variable or SafeData object.
    if hasattr(templatevar, 'var'):
        templatevar = templatevar.var
        if isinstance(templatevar, SafeData):
            # Literal in FilterExpression, can return.
            return is_true(templatevar)
        else:
            # Variable in FilterExpression, not going to work here.
            return None

    return is_true(templatevar)