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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 close(self):
 """This method closes the database correctly."""

        
        if self.filepath is not None:
            if path.isfile(self.filepath+'.lock'):
                remove(self.filepath+'.lock')
            self.filepath = None
            self.read_only = False
            self.lock()
            return True
        else:
            raise KPError('Can\'t close a not opened file')