Python 3, <strike>44</strike> <strike>43</strike> 41 Bytes
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Here's my implementation of this challenge with greatly appreciated help from the comments:

`print("".join(map(lambda x:x*2,input())))`

[Try it online!](https://tio.run/##K6gsycjPM/7/v6AoM69EQ0lJLys/M08jN7FAIycxNyklUaHCqkLLSCczr6C0REMTCP7/d8kvTcpJVSguSE3MVgQA)

Description
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It works by separating the script using pythons map function to grab every character in the inputted string then multiplying them by 2 and joining them back together after it is converted to a map using an empty string then joining every element to it.

edit: thanks to pxeger for suggesting to remove unnecessary spaces and thanks to Wheat Wizard ♦ for suggesting to remove the quotes from the input.