input: Write a python function to process the text by making an API request and returning the category.
  assert process_text('example text') == 'category1'
  assert process_text('another example') == 'category2'
  assert process_text('yet another example') == 'category3'
output: import requests
  
  def process_text(text):
      url = "https://api.example.com/categorize"
      payload = {'text': text}
      response = requests.post(url, json=payload)
      
      if response.status_code == 200:
          return response.json().get('category')
      else:
          return None