def get_grants(df):
    """Get list of grant numbers from dataframe.

    Assumptions:
        Dataframe has column called 'grantNumber'

    Returns:
        set: valid grant numbers, e.g. non-empty strings
    """

    print(f"Querying for grant numbers...", end="")
    grants = set(df.grantNumber.dropna())
    print(f"{len(grants)} found\n")
    return list(sorted(grants))