ToDo Line 15: Remove auxiliary classes about piconnect

[Hugovdberg]

Another way is to use pd.to_numeric(data, errors='coerce'), this will convert all non-numeric values to NaN. I'd rather not change this because there might be good reasons to keep the enumeration values, and some series might perhaps contain only non-numeric values. I often apply some pattern like this:

with PI.PIServer() as server:
    point = server.search('*')[0]
    data = point.recorded_values('-7d', '*')
    data = data.to_frame()
    data['values'] = pd.to_numeric(data[point.tag], errors='coerce')
    data.loc[data['values'].isna(), 'messages'] = data.loc[data['values'].isna(), point.tag].apply(str)