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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 start_block(self,stylestack=None):
 """ starts a block entity with an optional style definition """

        if self.dirty:
            self.escpos._raw('\n')
            self.dirty = False
        self.stack.append('block')
        if stylestack:
            self.style(stylestack)