Replace assert with the difference of values

Use math.isclose() to check whether two numbers are considered close. The function already takes into account the absolute values of the given numbers.

The following formula is used to compare the values: abs(a-b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)

source : https://docs.python.org/3/library/math.html#math.isclose

Conclusion: changes that meet the code review condition

tests/test_recog.py

@@ -1,6 +1,7 @@
 """Module with library tests"""
 from pathlib import Path
 import pytest
+import math
 import pygats.recog as rec
 import pygats.pygats as pyg
 from pygats.formatters import MarkdownFormatter as MD
@@ -99,4 +100,4 @@ def test_check_text_1(words_for_bg, capsys):
 def test_contrast(img_path, expected_value):
     img = Image.open(img_path)
     contrast = rec.contrast(img)
-    assert (contrast - expected_value) < 1e-9
+    assert math.isclose(contrast, expected_value, rel_tol=1e-09, abs_tol=0.0)