plan: document 'basic_rate'

plan.py

@@ -4,8 +4,11 @@ import math
 import fractions
 import collections
 
+from typing import Dict
+
 import satisfactory
 
+
 def calculate_rates(recipes, remain):
     required_items = collections.defaultdict(fractions.Fraction)
 
@@ -37,7 +40,12 @@ def calculate_rates(recipes, remain):
     return required_items
 
 
-def basic_rate(recipe):
+def basic_rate(recipe: Dict) -> fractions.Fraction:
+    """
+    Calculate the rate at which the item is crafted with the default recipe.
+    :param recipe:
+    :return:
+    """
     for output, count in recipe['output'].items():
         return fractions.Fraction(
             count, recipe['crafting_time']