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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 _base_placeholder(self):
 """ Return the notes master placeholder this notes slide placeholder inherits from, or |None| if no placeholder of the matching type is present. """

        notes_master = self.part.notes_master
        ph_type = self.element.ph_type
        return notes_master.placeholders.get(ph_type=ph_type)