attribute
T_co
PythonT_co = TypeVar('T_co', covariant=True)Random-access record sources.
T_coattributeDataSourceclassRecords addressed by index, such as a list or a Grain source.T_co = TypeVar('T_co', covariant=True)Records addressed by index, such as a list or a Grain source.
DataSource()Records addressed by index, such as a list or a Grain source.
source[i] must return the same record for the same i so that a seed fixes the order
and the augmentation of every epoch.