code: async def dump_blob(writer, elem, elem_type, params=None):
      
      elem_is_blob = isinstance(elem, x.BlobType)
      data = bytes(getattr(elem, x.BlobType.DATA_ATTR) if elem_is_blob else elem)
      await dump_varint(writer, len(elem))
      await writer.awrite(data)
docs: Dumps blob to a binary stream
  
      :param writer:
      :param elem:
      :param elem_type:
      :param params:
      :return: