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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(left, right):
 """ deep merge dictionary on the left with the one on the right. Fill in left dictionary with right one where the value of the key from the right one in the left one is missing or None. """

    if isinstance(left, dict) and isinstance(right, dict):
        for key, value in right.items():
            if key not in left:
                left[key] = value
            elif left[key] is None:
                left[key] = value
            else:
                left[key] = merge(left[key], value)
    return left