assertelem['bytes_read_compressed']<=elem['total_size_bytes_compressed'],"Bytes read ({}) more than total bytes ({}). It's a bug".format(elem['bytes_read_compressed'],elem['total_size_bytes_compressed'])
assert0.0<=elem['progress']<=1.0,"Progress shouldn't less than 0 and bigger than 1, got {}".format(elem['progress'])
assert0.0<=elem['elapsed'],"Elapsed time must be greater than 0, got {}".format(elem['elapsed'])
prev_progress=first_non_empty['progress']
foreleminfetches_result:
assertelem['progress']>=prev_progress,"Progress decreasing prev{}, next {}? It's a bug".format(prev_progress,elem['progress'])