chore(deps): update dependency multimethod to v2

requirements.txt

@@ -16,7 +16,7 @@ requests>=2.24.0, <3
 # Progress bar
 tqdm>=4.48.2, <5
 seaborn>=0.10.1, <0.14
-multimethod>=1.4, <2
+multimethod>=2, <3
 # metrics
 statsmodels>=0.13.2, <1
 # type checking