dtypeOfArrowFormat

Maps an Arrow format string to a DataType. The admitted flat set: the fixed-width kinds, "u"/"U" (utf8 and large_utf8; the 32-bit-offset form imports by widening), "tsn:" (nanosecond timestamps only - other units and timezones reject naming themselves) and "ttn" (time64[ns]). Durations, time32, dates, binary and the nested forms reject with the format in the error.