E303: Does not report, that a blank line between classes is needed, if they're defined inside an if statement

As stated in PEP8:

Separate top-level function and class definitions with two blank lines.

if __name__ == '__main__':
    class Pos:

        def __init__(self, x, y):
            self.x = x
            self.y = y

    class Lifetime:

        def __init__(self, lifetime):
            if lifetime < 0:
                raise ValueError('lifetime must be above 0')
            self.lifetime = lifetime

    class Name:

        def __init__(self, name):
            self.name = '"' + name + '"'