def _rectify_column(df):
    """remove string spaces from the column names of the PNBOIA dataframe

    Parameters
    ----------
    df : pandas dataframe

    Returns
    -------
    Pandas dataframe
    """
    df1 = df.copy(deep=True)
    k = {i: i.replace(' ', '') for i in df.keys()}
    df1 = df1.rename(columns=k)
    return df1