code: def variableMissingValue(ncVar):
      
      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
docs: 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.