Not able to access the elements inside the amp tags by using document.getElementById or document.getElementsByClassName

### Description

Not able to select the element inside the amp tags like amp-selector,amp-carousel by using the document.getElementById or document.getElementsByClassName. Always gets the null or empty array.

### Reproduction Steps

In code i am trying to access the select option. I want to make the city dropdown option selected based on the city user is in. I am getting null or empty array.

### Relevant Logs

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### Browser(s) Affected

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### OS(s) Affected

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### Device(s) Affected

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### AMP Version Affected

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