input: Write a python function to check if a variable name exceeds 20 characters.
  assert is_variable_name_too_long("short_name") == False
  assert is_variable_name_too_long("long_variable_name_is_not_good_practice") == True
  assert is_variable_name_too_long("medium_length_name") == False
output: def is_variable_name_too_long(variable_name):
      return len(variable_name) > 20