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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 check(mod):
 """Check the parsed ASDL tree for correctness. Return True if success. For failure, the errors are printed out and False is returned. """

    v = Check()
    v.visit(mod)

    for t in v.types:
        if t not in mod.types and not t in builtin_types:
            v.errors += 1
            uses = ", ".join(v.types[t])
            print('Undefined type {}, used in {}'.format(t, uses))
    return not v.errors