code: public boolean extractLinkValue(String colName, Map<String, Set<String>> mvLinkValueMap) {
          // Link column names always begin with '~'.
          if (colName.length() == 0 || colName.charAt(0) != '~') {
              return false;
          }
          
          // A '/' should separate the field name and object value.
          int slashInx = colName.indexOf('/');
          if (slashInx < 0) {
              return false;
          }
          
          // Extract the field name and ensure we know about this field.
          String fieldName = colName.substring(1, slashInx);
          
          // Extract the link value's target object ID and add it to the value set for the field.
          String linkValue = colName.substring(slashInx + 1);
          Set<String> valueSet = mvLinkValueMap.get(fieldName);
          if (valueSet == null) {
              // First value for this field.
              valueSet = new HashSet<String>();
              mvLinkValueMap.put(fieldName, valueSet);
          }
          valueSet.add(linkValue);
          return true;
      }
docs: Examine the given column name and, if it represents an MV link value, add it to the
  given MV link value map. If a link value is successfully extracted, true is returned.
  If the column name is not in the format used for MV link values, false is returned.
  
  @param colName        Column name from an object record belonging to this table (in
  string form).
  @param mvLinkValueMap Link value map to be updated if the column represents a valid
  link value.
  @return               True if a link value is extracted and added to the map; false
  means the column name was not a link value.