prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  problem with K.common._FLOATX
  I tried to run:
  
  ```
  a = K.random_normal((100, 200))
  ```
  
  and I got the error:
  
  ```
  /home/eders/python/Theano/theano/sandbox/rng_mrg.pyc in get_substream_rstates(self, n_streams, dtype, inc_rstate)
     1167 
     1168         """
  -> 1169         assert isinstance(dtype, str)
     1170         assert n_streams < 2**72
     1171         assert n_streams > 0
  
  AssertionError:
  ```
  
  I tried to print K.common._FLOATX to see what was going on and it is `u'float32'`. That little `u` upfront is making theano crash. I believe that when reading the type from json it was not converted to the right type of string. Anybody else had that problem? I'll check the code to see if I can fix it.
  
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `keras/backend/common.py`
  Content:
  ```
  1 import numpy as np
  2 
  3 # the type of float to use throughout the session.
  4 _FLOATX = 'float32'
  5 _EPSILON = 10e-8
  6 
  7 
  8 def epsilon():
  9     return _EPSILON
  10 
  11 
  12 def set_epsilon(e):
  13     global _EPSILON
  14     _EPSILON = e
  15 
  16 
  17 def floatx():
  18     return _FLOATX
  19 
  20 
  21 def set_floatx(floatx):
  22     global _FLOATX
  23     if floatx not in {'float32', 'float64'}:
  24         raise Exception('Unknown floatx type: ' + str(floatx))
  25     _FLOATX = floatx
  26 
  27 
  28 def cast_to_floatx(x):
  29     '''Cast a Numpy array to floatx.
  30     '''
  31     return np.asarray(x, dtype=_FLOATX)
  32
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/keras/backend/common.py b/keras/backend/common.py
  --- a/keras/backend/common.py
  +++ b/keras/backend/common.py
  @@ -22,6 +22,8 @@
       global _FLOATX
       if floatx not in {'float32', 'float64'}:
           raise Exception('Unknown floatx type: ' + str(floatx))
  +    if isinstance(floatx, unicode):
  +        floatx = floatx.encode('ascii')
       _FLOATX = floatx
  
verification_info: {"golden_diff": "diff --git a/keras/backend/common.py b/keras/backend/common.py\n--- a/keras/backend/common.py\n+++ b/keras/backend/common.py\n@@ -22,6 +22,8 @@\n     global _FLOATX\n     if floatx not in {'float32', 'float64'}:\n         raise Exception('Unknown floatx type: ' + str(floatx))\n+    if isinstance(floatx, unicode):\n+        floatx = floatx.encode('ascii')\n     _FLOATX = floatx\n", "issue": "problem with K.common._FLOATX\nI tried to run:\n\n```\na = K.random_normal((100, 200))\n```\n\nand I got the error:\n\n```\n/home/eders/python/Theano/theano/sandbox/rng_mrg.pyc in get_substream_rstates(self, n_streams, dtype, inc_rstate)\n   1167 \n   1168         \"\"\"\n-> 1169         assert isinstance(dtype, str)\n   1170         assert n_streams < 2**72\n   1171         assert n_streams > 0\n\nAssertionError:\n```\n\nI tried to print K.common._FLOATX to see what was going on and it is `u'float32'`. That little `u` upfront is making theano crash. I believe that when reading the type from json it was not converted to the right type of string. Anybody else had that problem? I'll check the code to see if I can fix it.\n\n", "before_files": [{"content": "import numpy as np\n\n# the type of float to use throughout the session.\n_FLOATX = 'float32'\n_EPSILON = 10e-8\n\n\ndef epsilon():\n    return _EPSILON\n\n\ndef set_epsilon(e):\n    global _EPSILON\n    _EPSILON = e\n\n\ndef floatx():\n    return _FLOATX\n\n\ndef set_floatx(floatx):\n    global _FLOATX\n    if floatx not in {'float32', 'float64'}:\n        raise Exception('Unknown floatx type: ' + str(floatx))\n    _FLOATX = floatx\n\n\ndef cast_to_floatx(x):\n    '''Cast a Numpy array to floatx.\n    '''\n    return np.asarray(x, dtype=_FLOATX)\n", "path": "keras/backend/common.py"}], "after_files": [{"content": "import numpy as np\n\n# the type of float to use throughout the session.\n_FLOATX = 'float32'\n_EPSILON = 10e-8\n\n\ndef epsilon():\n    return _EPSILON\n\n\ndef set_epsilon(e):\n    global _EPSILON\n    _EPSILON = e\n\n\ndef floatx():\n    return _FLOATX\n\n\ndef set_floatx(floatx):\n    global _FLOATX\n    if floatx not in {'float32', 'float64'}:\n        raise Exception('Unknown floatx type: ' + str(floatx))\n    if isinstance(floatx, unicode):\n        floatx = floatx.encode('ascii')\n    _FLOATX = floatx\n\n\ndef cast_to_floatx(x):\n    '''Cast a Numpy array to floatx.\n    '''\n    return np.asarray(x, dtype=_FLOATX)\n", "path": "keras/backend/common.py"}]}