added method to extract entity code from uri

biokb/utils.py

+def uri_to_code(uri: str) -> str:
+    """Translates URIs such as http://lcsb.uni.lu/biokb/entities/BTO_0001043 to BTO_0001043
+    
+    Arguments:
+        uri {str} -- [description]
+    
+    Returns:
+        str -- [description]
+    """
+    return uri.split('/')[-1]
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