Set_PythonType_class: don't use custom element_constructor

[jdemeyer]

If we want to remove the element_constructor argument to Parent.__init__, we should fix this:

cdef class Set_PythonType_class(Set_generic):
    [...]
    def __init__(self, theType):
        [...]
        Set_generic.__init__(self, element_constructor=theType, category=Sets())
        self._type = theType

This is easily done by defining an _element_constructor_ method.

This branch also changes "type" to "class" in the documentation and __repr__ to prepare for Python 3 (which consistently uses "class" in the __repr__ of types).

CC: @simon-king-jena

Component: misc

Author: Jeroen Demeyer

Branch/Commit: e6469c5

Reviewer: Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/23900

[jdemeyer]

Branch: u/jdemeyer/set_pythontype_class__don_t_use_custom_element_constructor

[jdemeyer]

Commit: e6469c5

[jdemeyer]

New commits:

e6469c5

Implement `_element_constructor_` for Set_PythonType_class

[jdemeyer]

Author: Jeroen Demeyer

[fchapoton]

comment:4

ok

[fchapoton]

Reviewer: Frédéric Chapoton

[vbraun]

Changed branch from u/jdemeyer/set_pythontype_class__don_t_use_custom_element_constructor to e6469c5