def get_child_projects_df(project_details_df):
    """
    Get details for projects that have an associated parent project ID.
    :param DataFrame project_details_df: the details for all projects
    :return DataFrame: child_projects_df
    """
    child_projects_df = project_details_df[project_details_df[
        'source_project_parent_id'].notna()]
    return child_projects_df
