import json


def read_alias_mapping(file_path):
    """Read and transform agent alias listing from a .json file."""
    if not file_path:
        return {}
    with open(file_path, "r") as mapping:
        data = mapping.read()
        obj = json.loads(data)
    aliases = {v: k for k, vs in obj.items() for v in vs}
    return aliases