input: Write a python function to calculate the weighted grade of a student given their scores in math, english, and biology, and the respective weights for each subject.
  assert calculate_weighted_grade(84, 89, 82, 0.3, 0.4, 0.3) == 85.10
  assert calculate_weighted_grade(90, 85, 80, 0.3, 0.4, 0.3) == 84.50
  assert calculate_weighted_grade(70, 75, 65, 0.2, 0.5, 0.3) == 72.00
output: def calculate_weighted_grade(math, english, biology, math_weight, english_weight, biology_weight):
      weighted_grade = (math * math_weight) + (english * english_weight) + (biology * biology_weight)
      return round(weighted_grade, 2)