code: def find_pair(self, crypto="", fiat="", verbose=False):
          
          self.fetch_pairs()
          if not crypto and not fiat:
              raise Exception("Fiat or Crypto required")
  
          def is_matched(crypto, fiat, pair):
              if crypto and not fiat:
                  return pair.startswith("%s-" % crypto)
              if crypto and fiat:
                  return pair == "%s-%s" % (crypto, fiat)
              if not crypto:
                  return pair.endswith("-%s" % fiat)
  
          matched_pairs = {}
          for Service, pairs in self._all_pairs.items():
              matched = [p for p in pairs if is_matched(crypto, fiat, p)]
              if matched:
                  matched_pairs[Service] = matched
  
          return matched_pairs
docs: This utility is used to find an exchange that supports a given exchange pair.