input: Write a function to classify emails into spam, ham, and uncertain categories.
  assert classify_email(['Special offer just for you', 'Welcome to our company', 'Meeting schedule']) == {'spam': 1, 'ham': 1, 'uncertain': 1}
  assert classify_email(['Discount on your next purchase', 'Company updates', 'Hello friend']) == {'spam': 1, 'ham': 1, 'uncertain': 1}
  assert classify_email(['Huge discount available', 'Welcome aboard', 'Important notice']) == {'spam': 1, 'ham': 1, 'uncertain': 1}
output: def classify_email(emails):
      categories = {'spam': 0, 'ham': 0, 'uncertain': 0}
      
      spam_keywords = ['special offer', 'discount', 'offer', 'purchase', 'available']
      ham_keywords = ['welcome', 'schedule', 'updates', 'hello', 'aboard']
      
      for email in emails:
          email_lower = email.lower()
          if any(spam_keyword in email_lower for spam_keyword in spam_keywords):
              categories['spam'] += 1
          elif any(ham_keyword in email_lower for ham_keyword in ham_keywords):
              categories['ham'] += 1
          else:
              categories['uncertain'] += 1
      
      return categories