Fix the syntax errors

tests/python/unittest/test_memory_opt.py

@@ -155,7 +155,7 @@ def grep_exec_memory_consumption(exec):
     import re  # We will be using regular expressions for grepping the model
                # memory consumption.
     alloc_line_pattern = re.compile("Total \d+ MB allocated")
-    for line in exec_debug_str():
+    for line in exec_debug_str:
         if alloc_line_pattern.match(line) is not None:
             return int(line.split()[1])
     assert False, "Unable to gerp the memory consumption numbers from the executor " \