title: tensorflow record with float numpy array
body: <p>I want to create tensorflow records to feed my model;
  so far I use the following code to store uint8 numpy array to TFRecord format;</p>
  
  <pre><code>def _int64_feature(value):
    return tf.train.Feature(int64_list=tf.train.Int64List(value=[value]))
  
  
  def _bytes_feature(value):
    return tf.train.Feature(bytes_list=tf.train.BytesList(value=[value]))
  
  
  def _floats_feature(value):
    return tf.train.Feature(float_list=tf.train.FloatList(value=[value]))
  
  
  def convert_to_record(name, image, label, map):
      filename = os.path.join(params.TRAINING_RECORDS_DATA_DIR, name + '.' + params.DATA_EXT)
  
      writer = tf.python_io.TFRecordWriter(filename)
  
      image_raw = image.tostring()
      map_raw   = map.tostring()
      label_raw = label.tostring()
  
      example = tf.train.Example(features=tf.train.Features(feature={
          'image_raw': _bytes_feature(image_raw),
          'map_raw': _bytes_feature(map_raw),
          'label_raw': _bytes_feature(label_raw)
      }))        
      writer.write(example.SerializeToString())
      writer.close()
  </code></pre>
  
  <p>which I read with this example code</p>
  
  <pre><code>features = tf.parse_single_example(example, features={
    'image_raw': tf.FixedLenFeature([], tf.string),
    'map_raw': tf.FixedLenFeature([], tf.string),
    'label_raw': tf.FixedLenFeature([], tf.string),
  })
  
  image = tf.decode_raw(features['image_raw'], tf.uint8)
  image.set_shape(params.IMAGE_HEIGHT*params.IMAGE_WIDTH*3)
  image = tf.reshape(image_, (params.IMAGE_HEIGHT,params.IMAGE_WIDTH,3))
  
  map = tf.decode_raw(features['map_raw'], tf.uint8)
  map.set_shape(params.MAP_HEIGHT*params.MAP_WIDTH*params.MAP_DEPTH)
  map = tf.reshape(map, (params.MAP_HEIGHT,params.MAP_WIDTH,params.MAP_DEPTH))
  
  label = tf.decode_raw(features['label_raw'], tf.uint8)
  label.set_shape(params.NUM_CLASSES)
  </code></pre>
  
  <p>and that's working fine. Now I want to do the same with my array "map" being a float numpy array, instead of uint8, and I could not find examples on how to do it;
  I tried the function _floats_feature, which works if I pass a scalar to it, but not with arrays;
  with uint8 the serialization can be done by the method tostring();</p>
  
  <p>How can I serialize a float numpy array and how can I read that back?</p>