Perf: Optimize string construction in section text parsing

[mohasarc]

This pull request optimizes string construction in the __init__ method by replacing section_text += line inside the file reading loop with list accumulation and .join().

The Issue: In Python, strings are immutable. Using += to append lines to the section_text string inside a while loop forces the interpreter to create a new string object and copy the old content for every line read. This results in quadratic time complexity O(n^2), which could potentially degrade performance when reading large data sections.

The Solution: I refactored the section text construction logic to accumulate lines in a list (section_lines) and use ''.join() at the end. This approach ensures linear time complexity O(n) because the total size of the final string is calculated once, and memory is allocated efficiently.

This is in line with standard python performance recommendation: https://peps.python.org/pep-0008/#programming-recommendations

[paulromano]

Thanks @mohasarc!