from typing import Dict
from typing import Any


def prefix_dict_keys(d: Dict[str, Any], prefix: str) -> Dict[str, Any]:
    """
    Returns a dictionary that's a copy of as ``d`` but with ``prefix``
    prepended to its keys.
    """
    result = {}  # type: Dict[str, Any]
    for k, v in d.items():
        result[prefix + k] = v
    return result