Again, chained comparisons. For any comparison operator (comparison operators are <, >, ==, >=, <=, <>, !=, 'is', 'not', 'is not', 'in' and 'not in'): x (o

Again, chained comparisons. For any comparison operator (comparison operators are <, >, ==, >=, <=, <>, !=, 'is', 'not', 'is not', 'in' and 'not in'): x (operator1) y (operator2) z is defined by the language as equivalent to (x (operator1) y) and (y (operator2) z) So 1 in [1] in [[1]] is equivalent to (1 in [1]) and ([1] in [[1]]) For any comparison operator