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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_positions(self, attr=None):
 """Get the positions data for the instrument :Optional: attr : string Position attribute to get (optional attributes: symbol, position, avgCost, account) :Retruns: positions : dict (positions) / float/str (attribute) positions data for the instrument """

        pos = self.parent.get_positions(self)
        try:
            if attr is not None:
                attr = attr.replace("quantity", "position")
            return pos[attr]
        except Exception as e:
            return pos