doc: Add additional special methods in class template
Mainly used in:
Datasetes
Iterators
Variable and Parameter
..
Special methods
-{% for item in ('__call__', '__enter__', '__exit__') %}
+{% for item in ('__call__', '__enter__', '__exit__', '__getitem__', '__setitem__', '__len__', '__next__', '__iter__', '__copy__') %}
{% if item in all_methods %}
.. automethod:: {{ item }}
{% endif %}
