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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 variableMissingValue(ncVar):
 """ Returns the missingData given a NetCDF variable Looks for one of the following attributes: _FillValue, missing_value, MissingValue, missingValue. Returns None if these attributes are not found. """

    attributes = ncVarAttributes(ncVar)
    if not attributes:
        return None # a premature optimization :-)

    for key in ('missing_value', 'MissingValue', 'missingValue', 'FillValue', '_FillValue'):
        if key in attributes:
            missingDataValue = attributes[key]
            return missingDataValue
    return None