bug fix

Author: Prerak Singh

pydatastructs/graphs/algorithms.py

@@ -11,7 +11,6 @@
 from pydatastructs.graphs.graph import Graph
 from pydatastructs.linear_data_structures.algorithms import merge_sort_parallel
 from pydatastructs import PriorityQueue
-from pydatastructs.graphs._backend.cpp._algorithms import bfs_adjacency_list, bfs_adjacency_matrix
 
 __all__ = [
     'breadth_first_search',
@@ -93,6 +92,7 @@ def breadth_first_search(
         return getattr(algorithms, func)(
             graph, source_node, operation, *args, **kwargs)
     else:
+        from pydatastructs.graphs._backend.cpp._algorithms import bfs_adjacency_list, bfs_adjacency_matrix
         if (graph._impl == "adjacency_list"):
             extra_args = args if args else ()
             return bfs_adjacency_list(graph, source_node, operation, extra_args)