Context

Same issue as described in #626
Issue solved for from_csv(), but same goes for all the other from_xxx()class methods, such as from_lines() and from_nadarray().

We want an exception to be raised when those class methods are called from an instance instead of the class, similar to the one pandas throws when read_csv()is being called from an instance:

import pandas as pd
df = pd.DataFrame()
df.read_csv()
>>> AttributeError: 'DataFrame' object has no attribute 'read_csv'