title: TypeError: expected string or bytes-like object 1
body: <p>This is the code which has some problem:</p>
  
  <pre><code>symbol_returns[i*num_samples + sample_iter] = tf.multiply(tf.cast(pos[i*num_samples + sample_iter], np.float32), y_[:,i])
  
  daily_returns_by_symbol_ = tf.concat( [tf.reshape(t, [-1,1],1) for t in symbol_returns.values()])
  </code></pre>
  
  <p>But there is some error, and I have no idea how to solve it.</p>
  
  <pre><code>Traceback (most recent call last):
    File "neural_net_exec.py", line 129, in &lt;module&gt;
      daily_returns_by_symbol_ = tf.concat( [tf.reshape(t, [-1,1],1) for t in symbol_returns.values()])
    File "neural_net_exec.py", line 129, in &lt;listcomp&gt;
      daily_returns_by_symbol_ = tf.concat( [tf.reshape(t, [-1,1],1) for t in symbol_returns.values()])
    File "/anaconda/envs/tensorflow/lib/python3.5/site-packages/tensorflow/python/ops/gen_array_ops.py", line 2619, in reshape
      name=name)
    File "/anaconda/envs/tensorflow/lib/python3.5/site-packages/tensorflow/python/framework/op_def_library.py", line 374, in apply_op
      with g.as_default(), ops.name_scope(name) as scope:
    File "/anaconda/envs/tensorflow/lib/python3.5/contextlib.py", line 59, in __enter__
      return next(self.gen)
    File "/anaconda/envs/tensorflow/lib/python3.5/site-packages/tensorflow/python/framework/ops.py", line 4522, in name_scope
      with g.as_default(), g.name_scope(n) as scope:
    File "/anaconda/envs/tensorflow/lib/python3.5/contextlib.py", line 59, in __enter__
      return next(self.gen)
    File "/anaconda/envs/tensorflow/lib/python3.5/site-packages/tensorflow/python/framework/ops.py", line 3171, in name_scope
      if not _VALID_OP_NAME_REGEX.match(name):
  TypeError: expected string or bytes-like object
  </code></pre>