provide me a python code that separates the text in the following text file named podcast_script.txt using seperators "Ravi: " and "Siri: " and assigns two separate voices to them using Amazon Polly and returns an mp3 file of the final podcast:

Siri: Hey folks, welcome back to another episode of "Grammar Galore"! Today, we've got a special guest with us—Ravi, the grammar guru himself. How's it going, Ravi?

Ravi: Doing great, Siri! Thanks for having me. Always excited to chat about the wonderful world of pronouns.

Siri: Haha, only you would call pronouns "wonderful"! But seriously, I heard you've got some essential tips for students prepping for the SAT?

Ravi: Absolutely! Mastering pronouns is like finding the secret shortcut in a video game—it can really boost your score in the Writing and Language section.

Siri: Ooh, secret shortcuts! Now you've got my attention. So, where should we start?

Ravi: Let's kick off with the different types of pronouns. There's quite a lineup: personal, possessive, relative, demonstrative, and reflexive pronouns.

Siri: That's a mouthful. Can you break it down like we're five?

Ravi: Sure thing! Think of personal pronouns as the stand-ins for people or things—like I, you, he, she, it, we, and they. They're the stunt doubles of grammar.

Siri: Haha, stunt doubles! So they jump in so the nouns can take a coffee break?

Ravi: Exactly! Then we've got possessive pronouns—mine, yours, his, hers, ours, theirs. They're all about showing ownership. Like labels on your stuff so your roommate doesn't "accidentally" borrow your hoodie again.

Siri: Ah, roommate dilemmas—I feel that on a personal level!

Ravi: Don't we all? Moving on, relative pronouns like who, whom, whose, which, and that connect clauses to nouns or other pronouns. They're like the glue holding your sentence together.

Siri: So they're the matchmakers of grammar?

Ravi: You could say that! Then there's demonstrative pronouns—this, that, these, those. They're used to point out specific things. Imagine pointing at pastries in a bakery: "I'll have those."

Siri: Mmm, pastries... Now I'm hungry. Thanks, Ravi.

Ravi: Anytime! Lastly, reflexive pronouns, which end with -self or -selves—myself, yourself, himself, herself. They reflect back to the subject. It's like taking a selfie in grammar form.

Siri: Grammar selfies—I love it! So, why are pronouns such a big deal on the SAT?

Ravi: Great question. One major focus is pronoun-antecedent agreement. The pronoun has to match the noun it's replacing in number and gender.

Siri: Right, like you wouldn't say "The dog wagged their tail." Unless... the dog has multiple tails?

Ravi: Haha, unless it's a mythical creature! But yes, it should be "its tail." Keeping singular with singular and plural with plural is key.

Siri: Got it. But what about when it's unclear who the pronoun is referring to?

Ravi: Ah, the dreaded ambiguity. The SAT loves to test that. If a sentence could make you wonder who "he" or "she" is, it's time to revise.

Siri: Like, "Alex talked to Jordan about his project." Wait—whose project?

Ravi: Exactly! It's ambiguous. Is it Alex's project or Jordan's? Clarifying prevents confusion.

Siri: Makes sense. Any tips for avoiding these pitfalls?

Ravi: One trick is to be specific. If in doubt, repeat the noun. It might feel repetitive, but clarity trumps style in formal writing.

Siri: Speaking of style, what's the deal with using "they" as a singular pronoun? I hear it all the time now.

Ravi: That's a hot topic! While "they" is increasingly accepted as a singular pronoun for gender neutrality, the SAT tends to stick with traditional rules. So, for the test, it's safer to use "he or she" with singular antecedents.

Siri: Ah, playing it safe with the grammar purists. Gotcha.

Ravi: Exactly. Also, watch out for pronoun case errors—using "I" when it should be "me," and vice versa.

Siri: Oh man, like when people say "Between you and I" instead of "Between you and me"?

Ravi: Yes! That one trips up many. A good test is to remove the other person from the sentence. You wouldn't say "Between I," right?

Siri: True. Unless you're a pirate—"Between I and the treasure..."

Ravi: Haha, maybe in Pirate Grammar 101!

Siri: So, any last-minute strategies for our SAT warriors out there?

Ravi: Practice is crucial. When reviewing sentences, always trace the pronouns back to their antecedents. Make sure they agree and that there's no confusion.

Siri: Kind of like being a grammar detective.

Ravi: Exactly! And if a sentence feels clunky because of pronouns, try rephrasing it without them. Sometimes that's the easiest fix.

Siri: Solid advice. Well, Ravi, you've given us a lot to ponder—pronouns, pastries, and pirates! Who knew grammar could be this entertaining?

Ravi: Glad to bring some fun to the mix!

Siri: Before we wrap up, any teaser for what you might share next time?

Ravi: Let's just say, we'll dive into the wild world of commas—those tiny marks that cause big headaches.

Siri: Ooh, the comma drama! Can't wait. Thanks again for joining us, Ravi.

Ravi: My pleasure, Siri. Happy studying, everyone!