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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 get_member_node(self, key):
 """Return the AST node for the given member, from the first tuple that serves it."""

    for tup, _ in self.lookups:
      if key in tup:
        return tup.get_member_node(key)
    raise RuntimeError('Key not found in composite tuple: %r' % key)