def drop_cols(df, drop):
    """Drop only exiosting cols from df.
    Raises no error, when cols do not exist."""
    if len(drop) > 0:
        # Find the keys to drop that are actually still in the df
        drop = list(set(drop).intersection(set(df.keys())))
        if len(drop) > 0:
            df = df.drop(drop, axis=1)
    return df