code: def contrast(
      image: Union[str, Image.Image],
      output_path: Optional[str] = None,
      factor: float = 1.0,
      metadata: Optional[List[Dict[str, Any]]] = None,
      bboxes: Optional[List[Tuple]] = None,
      bbox_format: Optional[str] = None,
  ) -> Image.Image:
      """
      Alters the contrast of the image
  
      @param image: the path to an image or a variable of type PIL.Image.Image
          to be augmented
  
      @param output_path: the path in which the resulting image will be stored.
          If None, the resulting PIL Image will still be returned
  
      @param factor: zero gives a grayscale image, values below 1.0 decreases contrast,
          a factor of 1.0 gives the original image, and a factor greater than 1.0
          increases contrast
  
      @param metadata: if set to be a list, metadata about the function execution
          including its name, the source & dest width, height, etc. will be appended
          to the inputted list. If set to None, no metadata will be appended or returned
  
      @param bboxes: a list of bounding boxes can be passed in here if desired. If
          provided, this list will be modified in place such that each bounding box is
          transformed according to this function
  
      @param bbox_format: signifies what bounding box format was used in `bboxes`. Must
          specify `bbox_format` if `bboxes` is provided. Supported bbox_format values are
          "pascal_voc", "pascal_voc_norm", "coco", and "yolo"
  
      @returns: Image.Image - Augmented PIL Image
      """
      image = imutils.validate_and_load_image(image)
  
      func_kwargs = imutils.get_func_kwargs(metadata, locals())
      src_mode = image.mode
  
      enhancer = ImageEnhance.Contrast(image)
      aug_image = enhancer.enhance(factor)
  
      imutils.get_metadata(
          metadata=metadata,
          function_name="contrast",
          aug_image=aug_image,
          **func_kwargs,
      )
  
      return imutils.ret_and_save_image(
          aug_image, output_path, src_mode
      )
  
imports: import io
  import math
  import os
  import pickle
  from copy import deepcopy
  from typing import Any, Callable, Dict, List, Optional, Tuple, Union
  import numpy
  from augly import utils
  from augly.image import utils
  from augly.image.utils.bboxes import spatial_bbox_helper
  from PIL import Image, ImageDraw, ImageEnhance, ImageFilter, ImageFont
label_desc: Use image node_id 8 for calling a global function with example usage: contrast(image, output_path, factor, metadata, bboxes, bbox_format) and returns: imutils