fix: API params are correctly extracted

[nikkothari22]

Earlier, the logic to find the function definition string was to go from the first mention of "def" to the first mention of ":" after the def index.

With type annotations, this means that a function like this

def add(a: int, b:int):

  #Add logic here

would give a function def like: add(a which is incorrect.

Two changes made:

1. For the ending index, look for ): instead of just the colon since that will signal the end of the function definition.
2. API Def is extracted until the last index of "):" + 1 to cover the last character.

This ensures that all params are covered.