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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def append(self, text, afterline=None):
 """Append text to the current buffer. Args: text (str or Sequence[str]):
 One or many lines of text to append. afterline (Optional[int]):
 Line number to append after. If 0, text is prepended before the first line; if ``None``, at end of the buffer. """

        if afterline:
            self._vim.current.buffer.append(text, afterline)
        else:
            self._vim.current.buffer.append(text)