code: def _get_converter(self, converter_str):
          
          ret = None
          if converter_str is not None:
              converter_desc_list = converter_str.split('.')
              if len(converter_desc_list) == 1:
                  converter = converter_desc_list[0]
                  # default to `converter`
                  ret = getattr(cvt, converter, None)
  
                  if ret is None:
                      # try module converter
                      ret = self.get_converter(converter)
  
                  if ret is None:
                      ret = self.get_resource_clz_by_name(converter)
  
                  if ret is None:
                      ret = self.get_enum_by_name(converter)
  
                  if ret is None:
                      # try parser config
                      ret = self.get(converter)
  
              if ret is None and converter_str is not None:
                  raise ValueError(
                      'Specified converter not supported: {}'.format(
                          converter_str))
          return ret
docs: find converter function reference by name
  
          find converter by name, converter name follows this convention:
  
              Class.method
  
          or:
  
              method
  
          The first type of converter class/function must be available in
          current module.
          The second type of converter must be available in `__builtin__`
          (or `builtins` in python3) module.
  
          :param converter_str: string representation of the converter func
          :return: function reference