Resolve "Operation Traversing"

Implemented the traverse method for an operation. This creates a generator with start point in the given operation. The traverse method uses BFS. Closes #11 (closed)

b_asic/utilities.py

+"""@package docstring
+B-ASIC Operation Module.
+TODO: More info.
+"""
+
 from typing import List
 from collections import deque
 
 from b_asic.operation import Operation
 
 def breadth_first_search(start: Operation) -> List[Operation]:
-        """Use breadth first search to traverse the operation tree."""
-        visited: List[Operation] = [start]
-        queue = deque([start])
-        while queue:
-            operation = queue.popleft()
-            yield operation
-            for n_operation in operation.neighbours:
-                if n_operation not in visited:
-                    visited.append(n_operation)
-                    queue.append(n_operation)
+    """Use breadth first search to traverse the operation tree."""
+    visited: List[Operation] = [start]
+    queue = deque([start])
+    while queue:
+        operation = queue.popleft()
+        yield operation
+        for n_operation in operation.neighbours:
+            if n_operation not in visited:
+                visited.append(n_operation)
+                queue.append(n_operation)