input: Write a function to perform sentiment analysis on product reviews using natural language processing techniques like tokenization, stopword removal, lemmatization, and feature extraction with CountVectorizer, followed by training a classification model. The function should accept a dataset of reviews and their corresponding sentiments, process the text to generate features, split the data into training and test sets, train a Naive Bayes classifier, and return the classification report.
  
  def sentiment_analysis_on_reviews(data):
      import numpy as np
      import pandas as pd
      import nltk
      from nltk.tokenize import word_tokenize
      import matplotlib.pyplot as plt
      from nltk.corpus import stopwords
      from nltk.stem import WordNetLemmatizer 
      from sklearn.feature_extraction.text import CountVectorizer
      from sklearn.model_selection import train_test_split
      from sklearn.naive_bayes import MultinomialNB
      from sklearn.metrics import classification_report
      
      # Tokenise the texts
      data['tokenised'] = data['review'].apply(word_tokenize)
      
      # Remove stopwords
      stop_words = set(stopwords.words('english'))
      data['filtered'] = data['tokenised'].apply(lambda x: [val for val in x if val not in stop_words])
      
      # Normalize words
      wordnet_lemmatizer = WordNetLemmatizer()
      data['normalised'] = data['filtered'].apply(lambda x: [wordnet_lemmatizer.lemmatize(val) for val in x])
      
      # Generate features using CountVectorizer
      cv = CountVectorizer()
      data['features'] = cv.fit_transform(data['normalised'].astype('str')).toarray()
      
      # Split into training and test sets
      X = data['features']
      y = data['sentiment']
      X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)
      
      # Train model
      model = MultinomialNB(alpha=0.1)
      model.fit(X_train, y_train)
      
      # Predict using the test set
      predictions = model.predict(X_test)
      
      # Generate a classification report
      report = classification_report(y_test, predictions)
      return report
  
  assert sentiment_analysis_on_reviews(pd.DataFrame({'review': ['This product is amazing!', 'I hate this!', 'I love it!'], 'sentiment': ['positive', 'negative', 'positive']}))
  assert sentiment_analysis_on_reviews(pd.DataFrame({'review': ['I am neutral about this.', 'Not bad, but not great either.'], 'sentiment': ['neutral', 'neutral']}))
output: def sentiment_analysis_on_reviews(data):
      import numpy as np
      import pandas as pd
      import nltk
      from nltk.tokenize import word_tokenize
      from nltk.corpus import stopwords
      from nltk.stem import WordNetLemmatizer 
      from sklearn.feature_extraction.text import CountVectorizer
      from sklearn.model_selection import train_test_split
      from sklearn.naive_bayes import MultinomialNB
      from sklearn.metrics import classification_report
      
      # Tokenise the texts
      data['tokenised'] = data['review'].apply(word_tokenize)
      
      # Remove stopwords
      stop_words = set(stopwords.words('english'))
      data['filtered'] = data['tokenised'].apply(lambda x: [val for val in x if val not in stop_words])
      
      # Normalize words
      wordnet_lemmatizer = WordNetLemmatizer()
      data['normalised'] = data['filtered'].apply(lambda x: [wordnet_lemmatizer.lemmatize(val) for val in x])
      
      # Generate features using CountVectorizer
      cv = CountVectorizer()
      data['features'] = cv.fit_transform(data['normalised'].astype('str')).toarray()
      
      # Split into training and test sets
      X = data['features']
      y = data['sentiment']
      X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)
      
      # Train model
      model = MultinomialNB(alpha=0.1)
      model.fit(X_train, y_train)
      
      # Predict using the test set
      predictions = model.predict(X_test)
      
      # Generate a classification report
      report = classification_report(y_test, predictions)
      return report