code: def select_chain(self, chain_urls: Dict[str, List[str]]) -> Tuple[str, List[str]]:
          
          chain_name = self.scenario.chain_name
          if chain_name in ('any', 'Any', 'ANY'):
              chain_name = random.choice(list(chain_urls.keys()))
  
          log.info('Using chain', chain=chain_name)
          try:
              return chain_name, chain_urls[chain_name]
          except KeyError:
              raise ScenarioError(
                  f'The scenario requested chain "{chain_name}" for which no RPC-URL is known.',
              )
docs: Select a chain and return its name and RPC URL.
  
          If the currently loaded scenario's designated chain is set to 'any',
          we randomly select a chain from the given `chain_urls`.
          Otherwise, we will return `ScenarioRunner.scenario.chain_name` and whatever value
          may be associated with this key in `chain_urls`.
  
          :raises ScenarioError:
              if ScenarioRunner.scenario.chain_name is not one of `('any', 'Any', 'ANY')`
              and it is not a key in `chain_urls`.