Write a python function to remove the characters which have odd index values of a given string.
def odd_values_string(str):
  result = "" 
  for i in range(len(str)):
    if i % 2 == 0:
      result = result + str[i]
  return result
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a python function to remove the characters which have odd index values of a given string.
def odd_values_string(str):
  result = "" 
  for i in range(len(str)):
    if i % 2 == 0:
      result = result + str[i]
  return result[/INST]assert odd_values_string('abcdef') == 'ace'
assert odd_values_string('python') == 'pto'
assert odd_values_string('data') == 'dt'</s>