text: Title: [FEA] validator
  Body: **Is your feature request related to a problem? Please describe.**
  
  A recent viz had some null titles -- would help to check validate somehow!
  
  **Describe the solution you'd like**
  
  Ex: https://gist.github.com/lmeyerov/423df6b3b5bd85d12fd74b85eca4a17a
  
  - nodes not in edges
  - edges referencing non-existent nodes
  - na nodes/edges
  - if colors/sizes/icons/titles, NA vals
  - if no title and defaulting to guess title, NAs there
  