Update lz78.py

adding error handling and more tests

Author: Ahmed99125

compression/lz78.py

@@ -53,14 +53,19 @@ def compress(self, text: str) -> list[Token]:
           '[(0, a), (1, c), (1, a), (0, c), (1, b), (4, a), (0, b), (3, a)]'
           >>> str(lz78_compressor.compress(""))
           '[]'
-          >>> str(lz78_compressor.compress([]))
-          '[]'
-          >>> str(lz78_compressor.compress({}))
-          '[]'
+          >>> lz78_compressor.compress([])
+          Traceback (most recent call last):
+          TypeError: Expected string.
+          >>> lz78_compressor.compress({})
+          Traceback (most recent call last):
+          TypeError: Expected string.
           >>> len("ababc") >= len(lz78_compressor.compress("ababc"))
           True
         """
 
+        if not isinstance(text, str):
+            raise TypeError("Expected string.")
+
         phrase_dict = {}
         tokens = []
         code = 1