<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _GetIdentifierMappings(self, parser_mediator, cache, database):
 """Retrieves the identifier mappings from SruDbIdMapTable table. In the SRUM database individual tables contain numeric identifiers for the application ("AppId") and user identifier ("UserId"). A more descriptive string of these values can be found in the SruDbIdMapTable. For example the numeric value of 42 mapping to DiagTrack. This method will cache the mappings of a specific SRUM database. Args: parser_mediator (ParserMediator):
 mediates interactions between parsers and other components, such as storage and dfvfs. cache (ESEDBCache):
 cache, which contains information about the identifiers stored in the SruDbIdMapTable table. database (pyesedb.file):
 ESE database. Returns: dict[int, str]: mapping of numeric identifiers to their string representation. """

    identifier_mappings = cache.GetResults('SruDbIdMapTable', default_value={})
    if not identifier_mappings:
      esedb_table = database.get_table_by_name('SruDbIdMapTable')
      if not esedb_table:
        parser_mediator.ProduceExtractionWarning(
            'unable to retrieve table: SruDbIdMapTable')
      else:
        identifier_mappings = self._ParseIdentifierMappingsTable(
            parser_mediator, esedb_table)

      cache.StoreDictInCache('SruDbIdMapTable', identifier_mappings)

    return identifier_mappings