text: Title: Static Type Hinting: `dataprofiler/reports/graphs.py`
  Body: **Is your feature request related to a problem? Please describe.**
  Improve the project in the area of 
  - Make collaboration and code contribution easier
  - Getting started with the code when a contributor is new to the code base
  
  **Describe the outcome you'd like:**
  Utilizing types from [mypy](https://mypy.readthedocs.io/en/stable/cheat_sheet_py3.html) documentation for python3, implement type hinting in `dataprofiler/reports/graphs.py`.
  
  **Additional context:**
  - [mypy](https://mypy.readthedocs.io/en/stable/cheat_sheet_py3.html) documentation
  - [Why use python types?](https://medium.com/vacatronics/why-you-should-consider-python-type-hints-770e5cb1570f)
  