cdm/src/main/java/ucar/nc2/dataset/NetcdfDataset.java
static public Set<Enhance> parseEnhanceMode(String enhanceMode) {
    if (enhanceMode == null) return null;
    
    switch (enhanceMode.toLowerCase()) {
      case "all":                    return getEnhanceAll();
      case "none":                   return getEnhanceNone();
      case "convertenums":           return EnumSet.of(Enhance.ConvertEnums);
      case "convertunsigned":        return EnumSet.of(Enhance.ConvertUnsigned);
      case "applyscaleoffset":       return EnumSet.of(Enhance.ApplyScaleOffset);
      case "convertmissing":         return EnumSet.of(Enhance.ConvertMissing);
      case "coordsystems":           return EnumSet.of(Enhance.CoordSystems);
      case "incompletecoordsystems": return EnumSet.of(Enhance.CoordSystems,
                                                       Enhance.IncompleteCoordSystems);
      // Legacy strings, retained for backwards compatibility:
      case "true":                   return getEnhanceAll();
      case "scalemissingdefer":      return getEnhanceNone();
      case "alldefer":               return EnumSet.of(Enhance.ConvertEnums, Enhance.CoordSystems);
      case "scalemissing":           return EnumSet.of(
              Enhance.ConvertUnsigned, Enhance.ApplyScaleOffset, Enhance.ConvertMissing);
      // Return null by default, since some valid strings actually return an empty set.
      default: return null;
    }
  }
static public Set<Enhance> parseEnhanceMode(String enhanceMode) {
    if (enhanceMode == null) return null;
    
    switch (enhanceMode.toLowerCase()) {
      case "all":                    return getEnhanceAll();
      case "none":                   return getEnhanceNone();
      case "convertenums":           return EnumSet.of(Enhance.ConvertEnums);
      case "convertunsigned":        return EnumSet.of(Enhance.ConvertUnsigned);
      case "applyscaleoffset":       return EnumSet.of(Enhance.ApplyScaleOffset);
      case "convertmissing":         return EnumSet.of(Enhance.ConvertMissing);
      case "coordsystems":           return EnumSet.of(Enhance.CoordSystems);
      case "incompletecoordsystems": return EnumSet.of(Enhance.CoordSystems,
                                                       Enhance.IncompleteCoordSystems);
      // Legacy strings, retained for backwards compatibility:
      case "true":                   return getEnhanceAll();
      case "scalemissingdefer":      return getEnhanceNone();
      case "alldefer":               return EnumSet.of(Enhance.ConvertEnums, Enhance.CoordSystems);
      case "scalemissing":           return EnumSet.of(
              Enhance.ConvertUnsigned, Enhance.ApplyScaleOffset, Enhance.ConvertMissing);
      // Return null by default, since some valid strings actually return an empty set.
      default: return null;
    }
  }
Retrieve the set of Enhancements that is associated with the given string.
<p/>
<table border="1">
<tr>  <th>String</th>  <th>Enhancements</th>  </tr>
<tr>  <td>All</td>  <td>ConvertEnums, ConvertUnsigned, ApplyScaleOffset, ConvertMissing, CoordSystems</td>  </tr>
<tr>  <td>None</td>                   <td> &lt;empty&gt; </td>                                    </tr>
<tr>  <td>ConvertEnums</td>           <td>ConvertEnums</td>                                       </tr>
<tr>  <td>ConvertUnsigned</td>        <td>ConvertUnsigned</td>                                    </tr>
<tr>  <td>ApplyScaleOffset</td>       <td>ApplyScaleOffset</td>                                   </tr>
<tr>  <td>ConvertMissing</td>         <td>ConvertMissing</td>                                     </tr>
<tr>  <td>CoordSystems</td>           <td>CoordSystems</td>                                       </tr>
<tr>  <td>IncompleteCoordSystems</td> <td>CoordSystems</td>                                       </tr>
<tr>  <td>true</td>                   <td>Alias for "All"</td>                                    </tr>
<tr>  <td>ScaleMissingDefer</td>      <td>Alias for "None"</td>                                   </tr>
<tr>  <td>AllDefer</td>               <td>ConvertEnums, CoordSystems</td>                         </tr>
<tr>  <td>ScaleMissing</td>           <td>ConvertUnsigned, ApplyScaleOffset, ConvertMissing</td>  </tr>
</table>

@param enhanceMode  a string from the above table.
@return  the set corresponding to {@code enhanceMode}, or {@code null} if there is no correspondence.