Added mat_flat module utility file

mat_flat.py

@@ -0,0 +1,19 @@
+
+from typing import List
+"""
+Flattens a 2D list (matrix) into a 1D list.
+Args:
+    M (List[List]): A two-dimensional list to be flattened.
+Returns:
+    List: A one-dimensional list containing all elements of the input matrix in row-major order.
+Example:
+    >>> flatten([[1, 2], [3, 4]])
+    [1, 2, 3, 4]
+    
+NOTE: If you add the mat_flat module to a project, call it with mat_flat.flatten(M).
+
+"""
+
+def flatten(M: List[List])-> List:
+    flat = [elem for row in M for elem in row]
+    return flat