def extract_items(input_text):
    """
    Extracts the list of items mentioned in the input text.

    :param input_text: A sentence describing the items.
    :return: A list of items mentioned in the input text.

    Example:
    Input: "I have a lettuce head, a head of broccoli, an onion, a stalk of celery, two carrots, a garlic, and a yam."
    Output: ['lettuce', 'broccoli', 'onion', 'celery', 'carrots', 'garlic', 'yam']
    """
    # Implementation assumed
    pass

def count_items(items_list):
    """
    Counts the total number of items based on the list provided.

    :param items_list: A list of items.
    :return: The total count of items.

    Example:
    Input: ['lettuce', 'broccoli', 'onion', 'celery', 'carrots', 'garlic', 'yam']
    Output: 7
    """
    # Implementation assumed
    pass

def calculate_total_items(input_text):
    """
    Calculates the total number of items based on the input text.

    :param input_text: A sentence describing the items.
    :return: The total count of items.

    Example:
    Input: "I have a lettuce head, a head of broccoli, an onion, a stalk of celery, two carrots, a garlic, and a yam."
    Output: 7
    """
    items = extract_items(input_text)
    total_items = count_items(items)
    return total_items
