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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 get_attribute_references(instring):
 """ Return a list of attribute references in the condition expression. attribute_reference ::= relation_name "." attribute_name | attribute_name :param instring: a condition expression. :return: a list of attribute references. """

    parsed = ConditionGrammar().conditions.parseString(instring)
    result = parsed if isinstance(parsed[0], str) else parsed[0]
    return result.attribute_reference.asList() if result.attribute_reference else []