class_docstr: Utility class to manage a set of ``ConfigItem`` and resolve the references between them.
  
  This class maintains a set of ``ConfigItem`` objects and their associated IDs.
  The IDs must be unique within this set. A string in ``ConfigItem``
  starting with ``@`` will be treated as a reference to other ``ConfigItem`` objects by ID.
  Since ``ConfigItem`` may have a nested dictionary or list structure,
  the reference string may also contain the separator ``::`` to refer to a substructure by
  key indexing for a dictionary or integer indexing for a list.
  
  In this class, resolving references is essentially substitution of the reference strings with the
  corresponding python objects. A typical workflow of resolving references is as follows:
  
      - Add multiple ``ConfigItem`` objects to the ``ReferenceResolver`` by ``add_item()``.
      - Call ``get_resolved_content()`` to automatically resolve the references. This is done (recursively) by:
          - Convert the items to objects, for those do not have references to other items.
              - If it is instantiable, instantiate it and cache the class instance in ``resolved_content``.
              - If it is an expression, evaluate it and save the value in ``resolved_content``.
          - Substitute the reference strings with the corresponding objects.
  
  Args:
      items: ``ConfigItem``s to resolve, this could be added later with ``add_item()``.
docstr: Match regular expression for the input string to find the references.
  The reference string starts with ``"@"``, like: ``"@XXX::YYY::ZZZ"``.
  
  Args:
      value: input value to match regular expression.
docstr_tok: ["Match","regular","expression","for","the","input","string","to","find","the","references",".","The","reference","string","starts","with","``","``","@","''","``",",","like",":","``","``","@","XXX",":",":YYY",":",":ZZZ","''","``",".","Args",":","value",":","input","value","to","match","regular","expression","."]
code: def match_refs_pattern(cls, value: str) -> dict[str, int]:
      """
      Match regular expression for the input string to find the references.
      The reference string starts with ``"@"``, like: ``"@XXX::YYY::ZZZ"``.
  
      Args:
          value: input value to match regular expression.
  
      """
      refs: dict[str, int] = {}
      # regular expression pattern to match "@XXX" or "@XXX::YYY"
      value = cls.normalize_id(value)
      result = cls.id_matcher.findall(value)
      value_is_expr = ConfigExpression.is_expression(value)
      for item in result:
          if value_is_expr or value == item:
              # only check when string starts with "$" or the whole content is "@XXX"
              id = item[len(cls.ref) :]
              refs[id] = refs.get(id, 0) + 1
      return refs
  
imports: from __future__ import annotations
  import re
  import warnings
  from collections.abc import Sequence
  from typing import Any, Iterator
  from monai.bundle.config_item import ConfigComponent, ConfigExpression, ConfigItem
  from monai.bundle.utils import ID_REF_KEY, ID_SEP_KEY
  from monai.utils import allow_missing_reference, look_up_option
label_desc: Use image node_id 11 for calling the ReferenceResolver obj's underlying member method code with example usage: obj.match_refs_pattern(cls, value) and returns: refs