private static List<MappedField> convertToLowercase(List<MappedField> fields) {
    return fields.stream()
        .map(
            mappedField -> {
              Set<String> lowercaseNames =
                  mappedField.names().stream()
                      .map(name -> name.toLowerCase(ENGLISH))
                      .collect(toImmutableSet());
              return MappedField.of(
                  mappedField.id(),
                  lowercaseNames,
                  convertToLowercase(mappedField.nestedMapping()));
            })
        .collect(toImmutableList());
  }
Create a new NameMapping with the same names but converted to lowercase.

@param nameMapping The original NameMapping, potentially containing non-lowercase characters
amoro-format-mixed/amoro-mixed-trino/src/main/java/org/apache/amoro/trino/unkeyed/IcebergPageSourceProvider.java