input: Write a python function to extract text from a PDF file using PyPDF2.
  assert extract_text_from_pdf("example1.pdf") == "Expected text from example1.pdf"
  assert extract_text_from_pdf("example2.pdf") == "Expected text from example2.pdf"
  assert extract_text_from_pdf("example3.pdf") == "Expected text from example3.pdf"
output: def extract_text_from_pdf(pdf_path):
      import PyPDF2
      
      with open(pdf_path, 'rb') as file:
          reader = PyPDF2.PdfFileReader(file)
          text = ''
          for page_num in range(reader.numPages):
              page = reader.getPage(page_num)
              text += page.extractText()
      return text