Python TSG: Chained assignment fails to be recognised  #402

repeat_hi = repeat_lo = repeat_avg = None

[
  (assignment
    left: (_) @pattern
    right: (_) @value)
  (with_item
    value:
      (as_pattern
        (_) @value
        alias: (as_pattern_target (_) @pattern)))
]
{
  edge @pattern.input -> @value.output
}

    0: Error executing statement edge @pattern.input -> @value.output at (1268, 3)
       src/stack-graphs.tsg:1268:3:
       1269 |   edge @pattern.input -> @value.output
            |   ^
       in stanza
       src/stack-graphs.tsg:1258:1:
       1258 | [
            | ^
       matching (assignment) node
       benchmark.py:121:9:
       121 |         repeat_hi = repeat_lo = repeat_avg = None 
           |         ^
    1: Evaluating edge sink
    2: Undefined scoped variable [syntax node assignment (121, 21)].output

[expression_statement](https://tree-sitter.github.io/tree-sitter/playground#) [0, 0] - [0, 41]
    [assignment](https://tree-sitter.github.io/tree-sitter/playground#) [0, 0] - [0, 41]
      left: [identifier](https://tree-sitter.github.io/tree-sitter/playground#) [0, 0] - [0, 9]
      right: [assignment](https://tree-sitter.github.io/tree-sitter/playground#) [0, 12] - [0, 41]
        left: [identifier](https://tree-sitter.github.io/tree-sitter/playground#) [0, 12] - [0, 21]
        right: [assignment](https://tree-sitter.github.io/tree-sitter/playground#) [0, 24] - [0, 41]
          left: [identifier](https://tree-sitter.github.io/tree-sitter/playground#) [0, 24] - [0, 34]
          right: [none](https://tree-sitter.github.io/tree-sitter/playground#) [0, 37] - [0, 41]