Bug : Unable to create merge skill from the skillset

I am trying to load the split the documents into chunks and create embeddings from that. To save some contextual information I want to concatenate the file name of the each document to its chunk at the starting of the chunk.

I want to have like '**chunk**: title: filename, chunk_data' in the field of chunk. how to achieve this. Normal text itself it is getting failed. Please help me resolve this

merge_skill = MergeSkill(
description="Skill to Merge text data via Skillset",
context= "/document/pages/*",
insertPreTag= " ",
insertPostTag= " ",
inputs=[
InputFieldMappingEntry(name="text", source="/document/pages/*"),
InputFieldMappingEntry(name="itemsToInsert", source="/document/metadata_storage_name"),
InputFieldMappingEntry(name="span", source=["0"]),
],
outputs=[
OutputFieldMappingEntry(name="mergedText", target_name="pageContent")
],
)

Start with the MergeSkill configuration and InputFieldMappingEntry sources shown in the issue, then compare how the skillset handles text, itemsToInsert, and span. Reproduce the reported failure with the shown configuration and confirm that the resulting pageContent contains the filename followed by each chunk.

Written by the indexing model from the issue text.