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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 validate_none(b):
 """Validate that None is given Parameters b: {None, 'none'} None or string (the case is ignored) Returns ------- None Raises ------ ValueError"""

    if isinstance(b, six.string_types):
        b = b.lower()
    if b is None or b == 'none':
        return None
    else:
        raise ValueError('Could not convert "%s" to None' % b)