Could not locate METIS dll

Question

in my code I was trying to import metis package. but I got the below error

File "C:\Users\hp\Desktop\process_data\ClusterGCN-master\src\clustering.py", line 1, in <module>
    import metis
  File "D:\anaconda3.4\lib\site-packages\metis.py", line 438, in <module>
    raise RuntimeError('Could not locate METIS dll. Please set the METIS_DLL environment variable to its full path.')
RuntimeError: Could not locate METIS dll. Please set the METIS_DLL environment variable to its full path.

do you know how to solve it?