class_docstr: This class is a Registry that stores information about the Accelerators.
  
  The Accelerators are mapped to strings. These strings are names that identify
  an accelerator, e.g., "gpu". It also returns Optional description and
  parameters to initialize the Accelerator, which were defined during the
  registration.
  
  The motivation for having a AcceleratorRegistry is to make it convenient
  for the Users to try different accelerators by passing mapped aliases
  to the accelerator flag to the Trainer.
  
  Example::
  
      @AcceleratorRegistry.register("sota", description="Custom sota accelerator", a=1, b=True)
      class SOTAAccelerator(Accelerator):
          def __init__(self, a, b):
              ...
  
      or
  
      AcceleratorRegistry.register("sota", SOTAAccelerator, description="Custom sota accelerator", a=1, b=True)
code: def __str__(self) -> str:
      return "Registered Accelerators: {}".format(
          ", ".join(self.available_accelerators())
      )
  
file_path: pytorch-lightning/src/lightning/fabric/accelerators/registry.py
imports: from typing import Any, Callable, Dict, List, Optional
  from typing_extensions import override
  from lightning.fabric.utilities.exceptions import MisconfigurationException
  from lightning.fabric.utilities.registry import _register_classes
label_desc: Use image node_id 5 for calling the _AcceleratorRegistry obj's underlying member method code with example usage: obj.__str__() and returns: str