Implement a function is_balanced(expression) that takes a string containing parentheses, curly braces, and square brackets,and determines whether the expression is balanced.

An expression is considered balanced if each opening bracket has a corresponding closing bracket in the correct order.

sample input:

expression1 = "([]{})"
expression2 = "([)]"

print(is_balanced(expression1)) 
print(is_balanced(expression2))

# True
# False

Write a function remove_duplicates(sequence) that takes a sequence (list or tuple) and returns a new sequence with duplicates removed while maintaining the original order of elements.

sample input:

input_sequence = [2, 3, 2, 4, 5, 3, 6, 7, 5]

result = remove_duplicates(input_sequence)

print(result) 

# [2, 3, 4, 5, 6, 7]

Implement a function word_frequency(sentence) that takes a sentence and returns a dictionary containing the frequency of each word in the sentence.

Ignore punctuation and consider words in a case-insensitive manner.

sample input:

sentence = "This is a test sentence? I'm sure this is a test sentence."

result = word_frequency(sentence) 

print(result) 

# {'this': 2, 'is': 2, 'a': 2, 'test': 2, 'sentence': 2, "i'm": 1, 'sure': 1}

Authored by Joy Anyango.