Use length_{a,b} again

specs/_features/eip7594/polynomial-commitments-sampling.md

@@ -246,8 +246,10 @@ def add_polynomialcoeff(a: PolynomialCoeff, b: PolynomialCoeff) -> PolynomialCoe
     """
     Sum the coefficient form polynomials ``a`` and ``b``.
     """
-    a, b = (a, b) if len(a) >= len(b) else (b, a)
-    return PolynomialCoeff([a[i] + (b[i] if i < len(b) else BLSFieldElement(0)) for i in range(len(a))])
+    length_a = len(a)
+    length_b = len(b)
+    a, b = (a, b) if length_a >= length_b else (b, a)
+    return PolynomialCoeff([a[i] + (b[i] if i < length_b else BLSFieldElement(0)) for i in range(length_a)])
 ```
 
 #### `neg_polynomialcoeff`