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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 insert(self, lines=None):
 """ Insert lines into the editor. Note: To insert before the first line, use :func:`~exa.core.editor.Editor.preappend` (or key 0); to insert after the last line use :func:`~exa.core.editor.Editor.append`. Args: lines (dict):
 Dictionary of lines of form (lineno, string) pairs """

        for i, (key, line) in enumerate(lines.items()):
            n = key + i
            first_half = self._lines[:n]
            last_half = self._lines[n:]
            self._lines = first_half + [line] + last_half