"""Identifies content gaps based on the primary content type and writing style.

This function analyzes the provided content type and writing style to determine potential gaps in the content strategy. It returns a list of suggested content types that could complement the existing strategy.

Args:
    content_type (Dict[str, Any]): A dictionary containing the primary content type. Expected to have a key 'primary_type' with values such as 'blog' or 'video'. Defaults to 'blog' if not provided.
    writing_style (Dict[str, Any]): A dictionary containing the writing style. Expected to have a key 'tone' with values such as 'professional' or 'casual'. Defaults to 'professional' if not provided.

Returns:
    List[str]: A list of suggested content types that could fill the identified gaps. The suggestions are based on the primary content type and the tone of the writing style.
"""
You should write code starting with:
from typing import Dict, List, Any

def _identify_content_gaps(content_type: Dict[str, Any], writing_style: Dict[str, Any]) -> List[str]:
    # TODO: Implement this function based on the docstring.
    pass

