input: 
  from typing import Dict, List
  
  def generate_table_of_contents(db_data: Dict[str, List[str]]) -> str:
      """ Generate an HTML page that displays a table of contents from the data stored in a database.
      The db_data is a dictionary where keys are section headers and values are lists of contents.
      >>> generate_table_of_contents({'Introduction': ['Overview', 'Purpose'], 'Methods': ['Data Collection', 'Analysis']})
      '<html><body><h1>Table of Contents</h1><ul><li>Introduction<ul><li>Overview</li><li>Purpose</li></ul></li><li>Methods<ul><li>Data Collection</li><li>Analysis</li></ul></li></ul></body></html>'
      """
  
output:     html_content = "<html><body><h1>Table of Contents</h1><ul>"
      for section, contents in db_data.items():
          html_content += f"<li>{section}<ul>"
          for content in contents:
              html_content += f"<li>{content}</li>"
          html_content += "</ul></li>"
      html_content += "</ul></body></html>"
      return html_content