SPDX license info from `requirements.txt`

Hi,

I am using requirements.txt to generate bom file. And the output is as follows. I would like to know how can I get the SPDX license id generated? thanks!

output:
```

2022-05-10T10:55:22.184404+00:00


CycloneDX
cyclonedx-bom
3.2.1


CycloneDX
cyclonedx-python-lib
2.3.0


https://github.com/CycloneDX/cyclonedx-python-lib/issues


https://cyclonedx.org


https://github.com/CycloneDX/cyclonedx-python-lib/actions


https://github.com/CycloneDX/cyclonedx-python-lib/blob/main/CHANGELOG.md


https://pypi.org/project/cyclonedx-python-lib/


https://github.com/CycloneDX/cyclonedx-python-lib/blob/main/LICENSE


https://cyclonedx.github.io/cyclonedx-python-lib/


https://github.com/CycloneDX/cyclonedx-python-lib







backports.entry-points-selectable
1.1.0
pkg:pypi/backports.entry-points-selectable@1.1.0


mypy-extensions
0.4.3
pkg:pypi/mypy-extensions@0.4.3


mccabe
0.6.1
pkg:pypi/mccabe@0.6.1


python-dateutil
2.8.1
pkg:pypi/python-dateutil@2.8.1


filelock
3.0.12
pkg:pypi/filelock@3.0.12


certifi
2021.5.30
pkg:pypi/certifi@2021.5.30


py
1.10.0
pkg:pypi/py@1.10.0


pydantic
1.8.2
pkg:pypi/pydantic@1.8.2


black
21.9b0
pkg:pypi/black@21.9b0


pytest
6.2.5
pkg:pypi/pytest@6.2.5


chardet
4.0.0
pkg:pypi/chardet@4.0.0


python-docx
0.8.11
pkg:pypi/python-docx@0.8.11


protobuf
3.17.2
pkg:pypi/protobuf@3.17.2


pyflakes
2.2.0
pkg:pypi/pyflakes@2.2.0


boto3
1.18.10
pkg:pypi/boto3@1.18.10


starlette
0.14.2
pkg:pypi/starlette@0.14.2


pycparser
2.20
pkg:pypi/pycparser@2.20


s3transfer
0.5.0
pkg:pypi/s3transfer@0.5.0


pyparsing
2.4.7
pkg:pypi/pyparsing@2.4.7


distlib
0.3.2
pkg:pypi/distlib@0.3.2


charset-normalizer
2.0.4
pkg:pypi/charset-normalizer@2.0.4


python-multipart
0.0.5
pkg:pypi/python-multipart@0.0.5


ddtrace
0.49.2
pkg:pypi/ddtrace@0.49.2


pytest-mock
3.6.1
pkg:pypi/pytest-mock@3.6.1


pytest-cov
2.12.1
pkg:pypi/pytest-cov@2.12.1


tenacity
7.0.0
pkg:pypi/tenacity@7.0.0


pymongo
3.11.4
pkg:pypi/pymongo@3.11.4


tox
3.24.3
pkg:pypi/tox@3.24.3


virtualenv
20.7.2
pkg:pypi/virtualenv@20.7.2


mangum
0.11.0
pkg:pypi/mangum@0.11.0


platformdirs
2.3.0
pkg:pypi/platformdirs@2.3.0


aiofiles
0.7.0
pkg:pypi/aiofiles@0.7.0


iniconfig
1.1.1
pkg:pypi/iniconfig@1.1.1


attrs
21.2.0
pkg:pypi/attrs@21.2.0


requests
2.25.1
pkg:pypi/requests@2.25.1


urllib3
1.26.5
pkg:pypi/urllib3@1.26.5


tomli
1.2.1
pkg:pypi/tomli@1.2.1


cryptography
3.4.7
pkg:pypi/cryptography@3.4.7


jmespath
0.10.0
pkg:pypi/jmespath@0.10.0


toml
0.10.2
pkg:pypi/toml@0.10.2


typing-extensions
3.10.0.0
pkg:pypi/typing-extensions@3.10.0.0


cachetools
4.2.2
pkg:pypi/cachetools@4.2.2


fastapi
0.65.1
pkg:pypi/fastapi@0.65.1


PyJWT
2.1.0
pkg:pypi/pyjwt@2.1.0


flake9
3.8.3.post2
pkg:pypi/flake9@3.8.3.post2


pycodestyle
2.6.0
pkg:pypi/pycodestyle@2.6.0


isort
5.9.3
pkg:pypi/isort@5.9.3


idna
2.10
pkg:pypi/idna@2.10


packaging
20.9
pkg:pypi/packaging@20.9


coverage
5.5
pkg:pypi/coverage@5.5


six
1.16.0
pkg:pypi/six@1.16.0


botocore
1.21.14
pkg:pypi/botocore@1.21.14


cffi
1.14.5
pkg:pypi/cffi@1.14.5


click
8.0.1
pkg:pypi/click@8.0.1


regex
2021.8.28
pkg:pypi/regex@2021.8.28


pathspec
0.9.0
pkg:pypi/pathspec@0.9.0


lxml
4.6.3
pkg:pypi/lxml@4.6.3


pluggy
1.0.0
pkg:pypi/pluggy@1.0.0


autoflake
1.4
pkg:pypi/autoflake@1.4

```

expected content included:
```
"license": {
"id": "Apache-2.0",
"text": {
"contentType": "text/plain",
"encoding": "base64",
```

Tái hiện quy trình tạo được báo cáo từ requirements.txt và kiểm tra đầu ra thành phần CycloneDX XML được hiển thị trong issue. Theo dõi cách siêu dữ liệu gói được thu thập và biểu diễn, sau đó xác minh rằng các thành phần được tạo có bao gồm các mã định danh giấy phép SPDX khi siêu dữ liệu đó khả dụng.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.