public static FieldPathEntry newMapLookupEntry(FieldValue lookupKey, DataType resultingDataType) {
        return new FieldPathEntry(lookupKey, resultingDataType);
    }
Creates a new field path entry that references a map or weighted set.

@param lookupKey The value of the key in the map or weighted set to recurse into.
@param resultingDataType The datatype of values in the map or weighted set.
@return The new field path entry
document/src/main/java/com/yahoo/document/FieldPathEntry.java