remove redundant variables and lines, fix typos

[Johnqczhang]

1. Remove unused variables and unused (or repeatedly imported) modules

2. Fix typos:

   • mask -> keypoint in keypoint_head.py: Line30 and in roi_heads.py: Line45
   • gor -> for in mask_head/inference.py: Line90
   • classification -> segmentation in roi_mask_feature_extractors.py: Line19

3. Add missing comment for argument discretization_size in mask_head/loss.py: Line22
   

   maskrcnn-benchmark/maskrcnn_benchmark/modeling/roi_heads/mask_head/loss.py

   Lines 11 to 23 in 19f6bb2

   	def project_masks_on_boxes(segmentation_masks, proposals, discretization_size):
   	"""
   	Given segmentation masks and the bounding boxes corresponding
   	to the location of the masks in the image, this function
   	crops and resizes the masks in the position defined by the
   	boxes. This prepares the masks for them to be fed to the
   	loss computation as the targets.
   	Arguments:
   	segmentation_masks: an instance of SegmentationMask
   	proposals: an instance of BoxList
   	discretization_size: spatial resolution of masks
   	"""

4. Remove incorrect comments in roi_mask_feature_extractors.py: Line23-28
   

   maskrcnn-benchmark/maskrcnn_benchmark/modeling/roi_heads/mask_head/roi_mask_feature_extractors.py

   Lines 22 to 28 in 6dfb4db

   	def __init__(self, cfg, in_channels):
   	"""
   	Arguments:
   	num_classes (int): number of output classes
   	input_size (int): number of channels of the input once it's flattened
   	representation_size (int): size of the intermediate representation
   	"""

5. Add two assertions when enabling sharing features from box_head for mask/keypoint head in roi_heads.py: Line19 and Line22
   

   maskrcnn-benchmark/maskrcnn_benchmark/modeling/roi_heads/roi_heads.py

   Lines 18 to 23 in 19f6bb2

   	if cfg.MODEL.MASK_ON and cfg.MODEL.ROI_MASK_HEAD.SHARE_BOX_FEATURE_EXTRACTOR:
   	assert cfg.MODEL.ROI_MASK_HEAD.POOLER_RESOLUTION == cfg.MODEL.ROI_BOX_HEAD.POOLER_RESOLUTION
   	self.mask.feature_extractor = self.box.feature_extractor
   	if cfg.MODEL.KEYPOINT_ON and cfg.MODEL.ROI_KEYPOINT_HEAD.SHARE_BOX_FEATURE_EXTRACTOR:
   	assert cfg.MODEL.ROI_KEYPOINT_HEAD.POOLER_RESOLUTION == cfg.MODEL.ROI_BOX_HEAD.POOLER_RESOLUTION
   	self.keypoint.feature_extractor = self.box.feature_extractor

[Johnqczhang]

Hi @fmassa, can you give a code review for my PR? Thanks!

[fmassa]

Sorry for the delay in reviewing.

It generally looks good, but there are a few things that should be reverted as they deserve more discussion

[Johnqczhang]

Hi @fmassa, I also fixed some other typos in #936 and some other changes (but not committed yet) regarding on similar issue with this PR. Should I merge it to this PR or leave it as another separate PR?

[Johnqczhang]

Hi @fmassa, the review changes have been done as you requested before, can we merge this PR now?