   last evaluation available in the variable "_". (It is stored in the
   "builtins" module, alongside built-in functions like "print".)

   Elsewhere, "_" is a regular identifier. It is often used to name
   “special” items, but it is not special to Python itself.

   Note:

     The name "_" is often used in conjunction with
     internationalization; refer to the documentation for the
     "gettext" module for more information on this convention.It is
     also commonly used for unused variables.

"__*__"
   System-defined names, informally known as “dunder” names. These
   names are defined by the interpreter and its implementation
   (including the standard library). Current system names are
   discussed in the Special method names section and elsewhere. More
   will likely be defined in future versions of Python.  *Any* use of
   "__*__" names, in any context, that does not follow explicitly
   documented use, is subject to breakage without warning.

"__*"
   Class-private names.  Names in this category, when used within the
   context of a class definition, are re-written to use a mangled form
   to help avoid name clashes between “private” attributes of base and
   derived classes. See section Identifiers (Names).
