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.

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))