input: Write a function to create a dictionary from a given list of numbers, where each key-value pair is in the form [x:x^2], with x being the key and x^2 being the value.
  assert create_dict([1, 2, 3, 4, 5])=={1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
  assert create_dict([0, -1, -2, -3])=={0: 0, -1: 1, -2: 4, -3: 9}
  assert create_dict([])=={}
  assert create_dict([5, -5])=={5: 25, -5: 25}
output: def create_dict(numbers):
      return {x: x**2 for x in numbers}