डेटा फ़्रेम को अननेस्ट करना

# Add one more step that unnests the tidied column
___ <- by_year_country %>%
  nest(-country) %>%
  mutate(model = map(data, ~ lm(percent_yes ~ year, data = .)),
         tidied = map(model, tidy))


# Print the resulting country_coefficients variable