step1c() turns terminal y to i when there is another vowel in the stem.

def step1c(self):
        """step1c() turns terminal y to i when there is another vowel in the stem."""
        if self.ends("y") and self.vowelinstem():
            self.b = self.b[: self.k] + "i" + self.b[self.k + 1 :]