def down_select(df,kv_lst) :
    """Filters rows given a set of values

    Given a DataFrame and a list of tuples columns (k) to values (v), this function
    filters out all rows where df[k] == v.

    Args:
        df (DataFrame): An input DataFrame.

        kv_list (list): A list of tuples of (column, value)

    Returns:
        DataFrame: Rows where all df[k] == v
    """
    for k,v in kv_lst :
        df=df[df[k]==v] 
    return df