from typing import Dict, Any, Optional, List


def export_plots(
    chart_spec: Dict[str, Any],
    formats: List[str] = ["png"],
    filename_base: str = "chart"
) -> Dict[str, Any]:
    """Export plots as PNG/SVG/PDF (placeholder spec).

    Note: This only returns a spec. Actual rendering/export should be handled
    by the frontend or a separate rendering service.
    """
    return {
        "type": "export",
        "formats": formats,
        "filename_base": filename_base,
        "chart": chart_spec,
    }
