Splits a dataframe of paths separated by NaNs into individual
    dataframes.

def split_dataframe(path_df):
    """
    Splits a dataframe of paths separated by NaNs into individual
    dataframes.
    """
    splits = np.where(path_df.iloc[:, 0].isnull())[0]+1
    return [df for df in np.split(path_df, splits) if len(df) > 1]