Returns all converters that take given value as an input value.

def GetConvertersByClass(value_cls):
    """Returns all converters that take given value as an input value."""
    try:
      return ExportConverter.converters_cache[value_cls]
    except KeyError:
      results = [
          cls for cls in itervalues(ExportConverter.classes)
          if cls.input_rdf_type == value_cls
      ]
      if not results:
        results = [DataAgnosticExportConverter]

      ExportConverter.converters_cache[value_cls] = results
      return results