def get_parent_projects_df(project_details_df):
    """
    Get details for projects that have an associated child project.
    :param DataFrame project_details_df: the details for all projects
    :return DataFrame: parent_projects_df
    """
    parent_projects_df = project_details_df[project_details_df[
        'source_project_parent_id'].isna()]
    return parent_projects_df
