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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 _compile_to_sklearn(self, expr):
 """Compile a DEAP pipeline into a sklearn pipeline. Parameters expr: DEAP individual The DEAP pipeline to be compiled Returns ------- sklearn_pipeline: sklearn.pipeline.Pipeline """

        sklearn_pipeline_str = generate_pipeline_code(expr_to_tree(expr, self._pset), self.operators)
        sklearn_pipeline = eval(sklearn_pipeline_str, self.operators_context)
        sklearn_pipeline.memory = self._memory
        return sklearn_pipeline