如何在没有tm包的情况下获得所有可能的2个单词组合及其频率

def get_word_combinations(text):
    words = text.split()
    combinations = {}
    
    for i in range(len(words)-1):
        word1 = words[i]
        word2 = words[i+1]
        combination = word1 + ' ' + word2
        
        if combination in combinations:
            combinations[combination] += 1
        else:
            combinations[combination] = 1
    
    return combinations

text = "This is a sample text for testing"
combinations = get_word_combinations(text)

for combination, frequency in combinations.items():
    print(combination, frequency)