fix: mypy 0.991 issues (#7988)

* fix: mypy 0.991 issues

* fix: invalid condition for base case

conversions/decimal_to_any.py

@@ -76,8 +76,9 @@ def decimal_to_any(num: int, base: int) -> str:
         div, mod = divmod(num, base)
         if base >= 11 and 9 < mod < 36:
             actual_value = ALPHABET_VALUES[str(mod)]
-            mod = actual_value
-        new_value += str(mod)
+        else:
+            actual_value = str(mod)
+        new_value += actual_value
         div = num // base
         num = div
         if div == 0:

data_structures/linked_list/__init__.py

@@ -49,7 +49,7 @@ class LinkedList:
         >>> print(linked_list)
         9 --> 14 --> 23
         """
-        if not self.is_empty:
+        if self.is_empty():
             return ""
         else:
             iterate = self.head

matrix/matrix_class.py

@@ -345,7 +345,7 @@ class Matrix:
         if other == 0:
             return self.identity()
         if other < 0:
-            if self.is_invertable:
+            if self.is_invertable():
                 return self.inverse() ** (-other)
             raise ValueError(
                 "Only invertable matrices can be raised to a negative power"