code: def construct_stable_id(
      parent_context,
      polymorphic_type,
      relative_char_offset_start,
      relative_char_offset_end,
  ):
      
      doc_id, _, parent_doc_char_start, _ = split_stable_id(parent_context.stable_id)
      start = parent_doc_char_start + relative_char_offset_start
      end = parent_doc_char_start + relative_char_offset_end
      return f"{doc_id}::{polymorphic_type}:{start}:{end}"
docs: Contruct a stable ID for a Context given its parent and its character
      offsets relative to the parent.