feat: add latex_figure_context_extractor_mapper operator

Add a new mapper operator that extracts figures and their citing context
from LaTeX source. It parses figure/figure*/wrapfigure environments,
handles subfigure environments and \subfigure/\subfloat commands, and
finds prose paragraphs that cite each figure via \ref/\cref/\autoref.

One input paper row fans out into N output figure rows (one per figure
or subfigure). Samples without figures are dropped.

Output fields: images, caption, label, citing_paragraphs,
parent_caption, parent_label.

Includes:
- Operator implementation with recursive nested-brace regex support
- Config entry in config_all.yaml
- Registration in mapper __init__.py
- Comprehensive unit tests (21 test cases)
- Operator documentation (EN/CN)

Author: asdweqwedf

data_juicer/config/config_all.yaml

@@ -198,6 +198,14 @@ process:
       model_params: {}                                        # Parameters for initializing the API model.
       sampling_params: {}                                     # Extra parameters passed to the API call. e.g {'temperature': 0.9, 'top_p': 0.95}
   - expand_macro_mapper:                                    # expand macro definitions in Latex text.
+  - latex_figure_context_extractor_mapper:                  # Extract figures and their citing context from LaTeX source.
+      citation_commands: ['\ref', '\cref', '\Cref', '\autoref']  # LaTeX reference commands to search for citing paragraphs.
+      paragraph_separator: '\n\n'                               # Pattern for splitting LaTeX text into paragraphs.
+      caption_key: 'caption'                                  # Output field name for the figure caption.
+      label_key: 'label'                                      # Output field name for the LaTeX label.
+      context_key: 'citing_paragraphs'                        # Output field name for citing paragraphs.
+      parent_caption_key: 'parent_caption'                    # Output field name for the parent figure's caption (subfigures only).
+      parent_label_key: 'parent_label'                        # Output field name for the parent figure's label (for grouping subfigures).
   - extract_entity_attribute_mapper:                        # Extract attributes for given entities from the text.
       api_model: 'gpt-4o'                                     # API model name.
       query_entities: ["孙悟空", "猪八戒"]                      # Entity list to be queried.

data_juicer/ops/mapper/__init__.py

@@ -47,6 +47,9 @@
 from .imgdiff_difference_caption_generator_mapper import (
     Difference_Caption_Generator_Mapper,
 )
+from .latex_figure_context_extractor_mapper import (
+    LatexFigureContextExtractorMapper,
+)
 from .mllm_mapper import MllmMapper
 from .nlpaug_en_mapper import NlpaugEnMapper
 from .nlpcda_zh_mapper import NlpcdaZhMapper
@@ -159,6 +162,7 @@
     "ImageSegmentMapper",
     "ImageTaggingMapper",
     "ImageTaggingVLMMapper",
+    "LatexFigureContextExtractorMapper",
     "MllmMapper",
     "NlpaugEnMapper",
     "NlpcdaZhMapper",