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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 _fusion_legacy_handler(_, __, tokens):
 """Handle a legacy fusion."""

    if RANGE_5P not in tokens:
        tokens[RANGE_5P] = {FUSION_MISSING: '?'}
    if RANGE_3P not in tokens:
        tokens[RANGE_3P] = {FUSION_MISSING: '?'}
    return tokens