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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 _split_python(python):
 """Split Python source into chunks. Chunks are separated by at least two return lines. The break must not be followed by a space. Also, long Python strings spanning several lines are not splitted. """

    python = _preprocess(python)
    if not python:
        return []
    lexer = PythonSplitLexer()
    lexer.read(python)
    return lexer.chunks