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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_lineplot(value):
 """Validate the value for the LinePlotter.plot formatoption Parameters value: None, str or list with mixture of both The value to validate"""

    if value is None:
        return value
    elif isinstance(value, six.string_types):
        return six.text_type(value)
    else:
        value = list(value)
        for i, v in enumerate(value):
            if v is None:
                pass
            elif isinstance(v, six.string_types):
                value[i] = six.text_type(v)
            else:
                raise ValueError('Expected None or string, found %s' % (v, ))
    return value