cdm/src/main/java/ucar/nc2/Structure.java
public Structure select( String varName) {
    List<String> memberNames = new ArrayList<>(1);
    memberNames.add(varName);
    return  select(memberNames);
  }
public Structure select( String varName) {
    List<String> memberNames = new ArrayList<>(1);
    memberNames.add(varName);
    return  select(memberNames);
  }
Create a subset of the Structure consisting only of the one member variable
@param varName name of member Variable
@return containing just that member