code: def _prepare_params(dirty_params, prefix=None):
      
      params = {}
      for k, v in dirty_params.items():
          if hasattr(v, "isoformat"):
              v = v.isoformat()
          elif isinstance(v, bool):
              # challonge.com only accepts lowercase true/false
              v = str(v).lower()
  
          if prefix:
              params["%s[%s]" % (prefix, k)] = v
          else:
              params[k] = v
  
      return params
docs: Prepares parameters to be sent to challonge.com.
  
      The `prefix` can be used to convert parameters with keys that
      look like ("name", "url", "tournament_type") into something like
      ("tournament[name]", "tournament[url]", "tournament[tournament_type]"),
      which is how challonge.com expects parameters describing specific
      objects.