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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 _merge_region_trees(self, dst_tree, src_tree, pid):
 """Merge conflicts occur if a folder in one tree is a file in the other. As the files are PIDs, this can only happen if a PID matches one of the geographical areas that the dataset covers and should be very rare. In such conflicts, the destination wins. """

        for k, v in list(src_tree.items()):
            # Prepend an underscore to the administrative area names, to make them
            # sort separately from the identifiers.
            # k = '_' + k
            if k not in dst_tree or dst_tree[k] is None:
                dst_tree[k] = {}
            dst_tree[k][pid] = None
            if v is not None:
                self._merge_region_trees(dst_tree[k], v, pid)