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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 plugin(tree, file_tokens):
 """Walk the tree and detect invalid escape sequences."""

    for token in file_tokens:
        if token[0] != STRING:  # token[0] == token.type
            continue
        # token[1] == token.string # python 3
        invalid_sequence_match = invalid_escape_sequence_match(token[1])
        if invalid_sequence_match:
            yield (
                token[2][0],  # line_number
                token[2][1],  # offset
                'IES: invalid escape sequence %s' %
                invalid_sequence_match.group(1),  # text
                None  # check # unused
            )