<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def join_comparisons(self, values, joiner, *, is_assignment=False, comp="="):
 """Generates comparisons with the value_comparisions method, and joins them with joiner. :is_assignment: if false, transform_op will be called on each comparison operator. """

    if isinstance(values, str):
      return values
    else:
      return joiner.join(self.value_comparisons(values, comp, is_assignment))