def _timestamp_from_json(value, field):
 if _not_null(value, field):
  return _datetime_from_microseconds((1000000.0 * float(value)))

def _timestamp_from_json ( value , field ) : if _not_null ( value , field ) : return _datetime_from_microseconds ( ( 1000000.0 * float ( value ) ) )
coerce value to a datetime .