input: Write a function to analyze and fix potential errors in a given Python function that attempts to modify a list while iterating over it. The fixed function should avoid unexpected behavior by copying the list before the iteration.
  
  def fix_expand_list(list):
      list_copy = list[:]
      for item in list_copy:
          list *= 2
  
  assert fix_expand_list([1, 2, 3])==[1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3]
  assert fix_expand_list([])==[]
  assert fix_expand_list([5])==[5, 5, 5]
  assert fix_expand_list([10, 20])==[10, 20, 10, 20, 10, 20, 10, 20]
output: def fix_expand_list(list):
      list_copy = list[:]
      for item in list_copy:
          list *= 2