docs: def revoc_info(briefs: Union[dict, Sequence[dict]], filt: dict = None) -> dict:
      """
      Given a cred-brief, cred-info or sequence of either, return a dict mapping pairs
      (revocation registry identifier, credential revocation identifier)
      to attribute name: (raw) value dicts.
  
      If the caller includes a filter of attribute:value pairs, retain only matching attributes.
  
      :param briefs: cred-brief/cred-info, or sequence thereof
      :param filt: dict mapping attributes to values of interest; e.g.,
  
      ::
  
          {
              'legalName': 'Flan Nebula',
              'effectiveDate': '2018-01-01',
              'endDate': None
          }
  
      :return: dict mapping (rev_reg_id, cred_rev_id) pairs to (raw) attributes; e.g.,
  
      ::
  
          {
              ('LjgpST2rjsoxYegQDRm7EL:4:LjgpST2rjsoxYegQDRm7EL:3:CL:17:tag:CL_ACCUM:1', '2'): {
                  'busId': '11121398',
                  'effectiveDate': '2010-10-10',
                  'endDate': '',
                  'id': '1',
                  'jurisdictionId': '1',
                  'legalName': 'The Original House of Pies',
                  'orgTypeId': '2'},
              ('LjgpST2rjsoxYegQDRm7EL:4:LjgpST2rjsoxYegQDRm7EL:3:CL:17:tag:CL_ACCUM:1', '3'): {
                  'busId': '11133333',
                  'effectiveDate': '2011-10-01',
                  'endDate': '',
                  'id': '2',
                  'jurisdictionId': '1',
                  'legalName': 'Planet Cake',
                  'orgTypeId': '1'}
          }
  
      """
  
      rv = {}
      for brief in iter_briefs(briefs):
          cred_info = brief.get('cred_info', {}) or brief  # briefs could be cred-infos or cred-briefs
          (rr_id, cr_id) = (cred_info['rev_reg_id'], cred_info['cred_rev_id'])
          if (rr_id, cr_id) in rv or rr_id is None or cr_id is None:
              continue
          if not filt:
              rv[(rr_id, cr_id)] = cred_info['attrs']
              continue
          if ({attr: str(filt[attr]) for attr in filt}.items() <= cred_info['attrs'].items()):
              rv[(rr_id, cr_id)] = cred_info['attrs']
  
      return rv