Remove unused imports. (#33)

* Remove unused collections import.

Author: tirkarthi

metaflow/datastore/datastore.py

@@ -4,7 +4,6 @@
 import time
 from hashlib import sha1
 from functools import partial
-from collections import Sequence
 
 try:
     # Python 2

metaflow/plugins/conda/conda_step_decorator.py

@@ -1,4 +1,3 @@
-import collections
 import os
 import sys
 from hashlib import sha1
@@ -235,4 +234,4 @@ def runtime_step_cli(self, cli_args, retry_count, max_user_code_retries):
             cli_args.entrypoint[0] = self.conda.python(self.env_id)
 
     def runtime_finished(self, exception):
-        shutil.rmtree(self.metaflow_home)
+        shutil.rmtree(self.metaflow_home)