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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 _grow_trees(self):
 """ Adds new trees to the forest according to the specified growth method. """

        if self.grow_method == GROW_AUTO_INCREMENTAL:
            self.tree_kwargs['auto_grow'] = True
        
        while len(self.trees) < self.size:
            self.trees.append(Tree(data=self.data, **self.tree_kwargs))