Create 2_new_data_model.md

[siatwangmin]

fix some typo

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Motivation

there are some typo at "mask_rcnn_r50_caffe_fpn_mstrain-poly_1x_balloon.py"  dataset_type = 'COCODataset'

Modification

there are some typo at "mask_rcnn_r50_caffe_fpn_mstrain-poly_1x_balloon.py"  dataset_type = 'COCODataset'

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMCls.
4. The documentation has been modified accordingly, like docstring or example tutorials.

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All committers have signed the CLA.

[codecov]

Codecov Report

Merging #6476 (9ef35c9) into dev (951996c) will decrease coverage by 0.11%.
The diff coverage is n/a.

❗ Current head 9ef35c9 differs from pull request most recent head 7a3ee06. Consider uploading reports for the commit 7a3ee06 to get more accurate results

@@            Coverage Diff             @@
##              dev    #6476      +/-   ##
==========================================
- Coverage   62.18%   62.06%   -0.12%     
==========================================
  Files         330      319      -11     
  Lines       26032    25314     -718     
  Branches     4436     4189     -247     
==========================================
- Hits        16187    15711     -476     
+ Misses       8971     8779     -192     
+ Partials      874      824      -50     

Flag	Coverage Δ
unittests	62.04% <ø> (-0.12%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmdet/core/evaluation/eval_hooks.py	61.11% <0.00%> (-20.71%)	⬇️
mmdet/core/bbox/assigners/sim_ota_assigner.py	76.14% <0.00%> (-3.86%)	⬇️
mmdet/models/utils/misc.py	92.85% <0.00%> (-3.58%)	⬇️
mmdet/datasets/wider_face.py	41.66% <0.00%> (-2.34%)	⬇️
mmdet/models/losses/focal_loss.py	67.27% <0.00%> (-2.07%)	⬇️
mmdet/datasets/pipelines/compose.py	78.57% <0.00%> (-1.43%)	⬇️
mmdet/datasets/dataset_wrappers.py	81.17% <0.00%> (-1.05%)	⬇️
mmdet/models/losses/gfocal_loss.py	96.49% <0.00%> (-0.85%)	⬇️
mmdet/datasets/voc.py	29.16% <0.00%> (-0.84%)	⬇️
mmdet/core/export/pytorch2onnx.py	14.03% <0.00%> (-0.78%)	⬇️
... and 111 more

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[ZwwWayne]

Kindly ping @siatwangmin , we can merge this PR after resolving comments.

[ZwwWayne]

Can be merged after resolving conflicts.

[OpenMMLab-Coodinator]

Hi siatwangmin！First of all, we want to express our gratitude for your significant PR in the MMDet project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.

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