class_docstr: The FormatManager is a singleton plugin factory.
  
  The format manager supports getting a format object using indexing (by
  format name or extension). When used as an iterator, this object
  yields all registered format objects.
  
  See also :func:`.help`.
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code: def __getitem__(self, name):
      warnings.warn(
          "The usage of `FormatManager` is deprecated and it will be "
          "removed in Imageio v3. Use `iio.imopen` instead.",
          DeprecationWarning,
          stacklevel=2,
      )
  
      if not isinstance(name, str):
          raise ValueError(
              "Looking up a format should be done by name or by extension."
          )
  
      if name == "":
          raise ValueError("No format matches the empty string.")
  
      # Test if name is existing file
      if Path(name).is_file():
          # legacy compatibility - why test reading here??
          try:
              return imopen(name, "r", legacy_mode=True)._format
          except ValueError:
              # no plugin can read the file
              pass
  
      config = _get_config(name.upper())
  
      try:
          return config.format
      except ImportError:
          raise ImportError(
              f"The `{config.name}` format is not installed. "
              f"Use `pip install imageio[{config.install_name}]` to install it."
          )
  
imports: import sys
  import warnings
  import contextlib
  import numpy
  from pathlib import Path
  from .None import Array, asarray
  from .request import ImageMode
  from ..config import known_plugins, known_extensions, PluginConfig, FileExtension
  from ..config.plugins import _original_order
  from .imopen import imopen
label_desc: Use image node_id 6 for calling the FormatManager obj's underlying member method code with example usage: obj.__getitem__(name) and returns: config, imopen