convert get AttributeError: 'OPCRelationship' object has no attribute 'relationships_path'

Hi 
I do install follow introduction and convert and get error:

D:\rac>pydocx --html d:\rac\pydocx-master\helloworld.docx d:\1.html

Traceback (most recent call last):
  File "c:\Python27\Scripts\pydocx-script.py", line 9, in <module>
    load_entry_point('PyDocX==0.3.16', 'console_scripts', 'pydocx')()
  File "c:\Python27\lib\site-packages\pydocx\__init__.py", line 24, in main
    html = Docx2Html(path_to_docx).parsed
  File "c:\Python27\lib\site-packages\pydocx\parsers\Docx2Html.py", line 58, in
parsed
    content = super(Docx2Html, self).parsed
  File "c:\Python27\lib\site-packages\pydocx\DocxParser.py", line 897, in parsed

    self._load()
  File "c:\Python27\lib\site-packages\pydocx\DocxParser.py", line 289, in _load
    package = WordprocessingMLPackage.load(self.path)
  File "c:\Python27\lib\site-packages\pydocx\DocxParser.py", line 138, in load
    file_handle=zip_file_handle,
  File "c:\Python27\lib\site-packages\pydocx\DocxParser.py", line 163, in _load
    root=root,
  File "c:\Python27\lib\site-packages\pydocx\DocxParser.py", line 235, in _load_
relationships
    root.relationships_path,
AttributeError: 'OPCRelationship' object has no attribute 'relationships_path'