How to remove the old dynet on Ubuntu?

I'm currently suffering the following issue when installing with GPU.

```bash
Python 3.5.2 (default, Nov 12 2018, 13:43:14)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import dynet
Traceback (most recent call last):
File "", line 1, in
File "/home/allan/.local/lib/python3.5/site-packages/dyNET-0.0.0-py3.5-linux-x86_64.egg/dynet.py", line 15, in
from _dynet import *
ImportError: /home/allan/.local/lib/python3.5/site-packages/dyNET-0.0.0-py3.5-linux-x86_64.egg/_dynet.cpython-35m-x86_64-linux-gnu.so: undefined symbol: _ZN5dynet13TextFileSaver4saveERKNS_19ParameterCollectionERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE
```

I searched for some solutions and some say it could be the problem that the old version is still there.
BTW, I'm building a GPU version of dynet

Start with the Python import traceback and the installed path `/home/allan/.local/lib/python3.5/site-packages/dyNET-0.0.0-py3.5-linux-x86_64.egg/`, then check how the GPU build was installed and whether an older DyNet remains. Reproduce `import dynet` after removing or replacing the old installation; done means the GPU build imports without the undefined-symbol error.

Written by the indexing model from the issue text.