"""Definition of check_env function."""

import os


def check_env(
    var_list: set[str],
) -> None:
    """Check necessary environment variables are set."""
    assert isinstance(var_list, set)
    assert all(isinstance(elem, str) for elem in var_list)
    # check that env vars are set
    missing_vars = []
    for env_var in var_list:
        if env_var not in os.environ:
            missing_vars.append(env_var)
    if len(missing_vars) > 0:
        raise OSError(f"environment variable(s) not set: {missing_vars}")