diff --git a/matrix/count_islands_in_matrix.py b/matrix/count_islands_in_matrix.py
index 64c595e84..9e98b4418 100644
--- a/matrix/count_islands_in_matrix.py
+++ b/matrix/count_islands_in_matrix.py
@@ -4,12 +4,43 @@
 
 
 class Matrix:  # Public class to implement a graph
-    def __init__(self, row: int, col: int, graph: list[list[bool]]) -> None:
-        self.ROW = row
-        self.COL = col
+    def __init__(self, graph: list[list[bool]]) -> None:
+        """
+        Initialise matrix with number of rows, columns, and graph.
+
+        >>> m = Matrix([[True, False, False, False],
+        ...              [True, False, True, False],
+        ...              [False, False, True, True]])
+        >>> m.ROW
+        3
+        >>> m.COL
+        4
+        >>> m.graph
+        [[True, False, False, False],
+        ...[True, False, True, False],
+        ...[False, False, True, True]]
+        """
         self.graph = graph
+        self.ROW = len(graph)
+        self.COL = len(graph[0])
 
     def is_safe(self, i: int, j: int, visited: list[list[bool]]) -> bool:
+        """
+        >>> visited = [[False, False, False],
+        ...             [False, False, False],
+        ...             [False, False, False]]
+        >>> m = Matrix([[True, False, False],
+        ...              [False, False, True],
+        ...              [False, False, True]])
+        >>> m.is_safe(0, 0, visited)
+        True
+        >>> m.is_safe(0, 2, visited)
+        False
+        >>> m.is_safe(-1, 2, visited)
+        False
+        >>> m.is_safe(1, 5, visited)
+        False
+        """
         return (
             0 <= i < self.ROW
             and 0 <= j < self.COL
@@ -18,7 +49,21 @@ class Matrix:  # Public class to implement a graph
         )
 
     def diffs(self, i: int, j: int, visited: list[list[bool]]) -> None:
-        # Checking all 8 elements surrounding nth element
+        """
+        Checking all 8 elements surrounding nth element.
+
+        >>> visited = [[False, False, False],
+        ...             [False, False, False],
+        ...             [False, False, False]]
+        >>> m = Matrix([[True, True, False],
+        ...              [False, True, False],
+        ...              [True, False, True]])
+        >>> m.diffs(0, 0, visited)
+        >>> visited
+        [[True, True, False],
+        ...[False, True, False],
+        ...[True, False, True]]
+        """
         row_nbr = [-1, -1, -1, 0, 0, 1, 1, 1]  # Coordinate order
         col_nbr = [-1, 0, 1, -1, 1, -1, 0, 1]
         visited[i][j] = True  # Make those cells visited
@@ -26,12 +71,24 @@ class Matrix:  # Public class to implement a graph
             if self.is_safe(i + row_nbr[k], j + col_nbr[k], visited):
                 self.diffs(i + row_nbr[k], j + col_nbr[k], visited)
 
-    def count_islands(self) -> int:  # And finally, count all islands.
+    def count_islands(self) -> int:
+        """
+        >>> m = Matrix([[True, True, False, False],
+        ...              [False, True, False, True],
+        ...              [True, False, False, True]])
+        >>> m.count_islands()
+        2
+        >>> m2 = Matrix([[True, True, False],
+        ...               [True, False, False],
+        ...               [False, False, True]])
+        >>> m2.count_islands()
+        2
+        """
         visited = [[False for j in range(self.COL)] for i in range(self.ROW)]
         count = 0
         for i in range(self.ROW):
             for j in range(self.COL):
-                if visited[i][j] is False and self.graph[i][j] == 1:
+                if not visited[i][j] and self.graph[i][j]:
                     self.diffs(i, j, visited)
                     count += 1
         return count