class_docstr: Core :py:class:`.PluginManager` class which manages registration
  of plugin objects and 1:N hook calling.
  
  You can register new hooks by calling :py:meth:`add_hookspecs(module_or_class)
  <.PluginManager.add_hookspecs>`.
  You can register plugin objects (which contain hooks) by calling
  :py:meth:`register(plugin) <.PluginManager.register>`.  The :py:class:`.PluginManager`
  is initialized with a prefix that is searched for in the names of the dict
  of registered plugin objects.
  
  For debugging purposes you can call :py:meth:`.PluginManager.enable_tracing`
  which will subsequently send debug information to the trace helper.
code: def _hookexec(self, hook, methods, kwargs):
      # called from all hookcaller instances.
      # enable_tracing will set its own wrapping function at self._inner_hookexec
      return self._inner_hookexec(hook, methods, kwargs)
  
imports: import inspect
  import sys
  from .None import _tracing
  from .callers import _Result
  from .hooks import HookImpl, _HookRelay, _HookCaller, normalize_hookimpl_opts
  import warnings
label_desc: Use image node_id 2 for calling the PluginManager obj's underlying member method code with example usage: obj._hookexec(hook, methods, kwargs) and returns: self