NameError: name 'TitlecaseExtension' is not defined

[engineervix]

I installed mdx_titlecase in a Python 3.6 virtual environment, alongside other third party markdown extensions. The output of pip freeze is as follows:

Markdown==3.0.1
MarkdownSuperscript==2.1.1
mdx-titlecase==1.2.0
titlecase==0.12.0

I ran the following command to transform my markdown to html:

python -m markdown -o html -x markdown.extensions.nl2br -x markdown.extensions.extra -x markdown.extensions.smarty -x 'mdx_superscript' -x 'mdx_titlecase' -f file.html file.md

I got the following error

Traceback (most recent call last):
  File "/usr/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/foobar/.virtualenvs/some_virtual_env/lib/python3.6/site-packages/markdown/__main__.py", line 144, in <module>
    run()
  File "/home/foobar/.virtualenvs/some_virtual_env/lib/python3.6/site-packages/markdown/__main__.py", line 138, in run
    markdown.markdownFromFile(**options)
  File "/home/foobar/.virtualenvs/some_virtual_env/lib/python3.6/site-packages/markdown/core.py", line 408, in markdownFromFile
    md = Markdown(**kwargs)
  File "/home/foobar/.virtualenvs/some_virtual_env/lib/python3.6/site-packages/markdown/core.py", line 100, in __init__
    configs=kwargs.get('extension_configs', {}))
  File "/home/foobar/.virtualenvs/some_virtual_env/lib/python3.6/site-packages/markdown/core.py", line 126, in registerExtensions
    ext = self.build_extension(ext, configs.get(ext, {}))
  File "/home/foobar/.virtualenvs/some_virtual_env/lib/python3.6/site-packages/markdown/core.py", line 181, in build_extension
    return module.makeExtension(**configs)
  File "/home/foobar/.virtualenvs/some_virtual_env/lib/python3.6/site-packages/mdx_titlecase/__init__.py", line 29, in makeExtension
    return TitlecaseExtension(**kwargs)
NameError: name 'TitlecaseExtension' is not defined

What could the problem be?