input: Write a function to return a list of characters from a given alphabet string. Each character should be included in the list exactly once, in the order they appear in the alphabet string. The function should handle any valid string passed as the alphabet parameter.
  assert identify_characters('ABCDEFGHIJKLMNOPQRSTUVWXYZ') == ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']
  assert identify_characters('abcdefghijklmnopqrstuvwxyz') == ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
  assert identify_characters('') == []
  assert identify_characters('1234567890') == ['1', '2', '3', '4', '5', '6', '7', '8', '9', '0']
  assert identify_characters('!@#$%^&*()') == ['!', '@', '#', '$', '%', '^', '&', '*', '(', ')']
output: def identify_characters(alphabet):
      return list(alphabet)