def concatenation(clean_list):
    """
    Concatenation example.
    Takes the processed list for your emails and concatenates any elements that are currently separate that you may
    wish to have as one element, such as dates.
    E.g. ['19', 'Feb', '2018'] becomes ['19 Feb 2018]
    Works best if the lists are similar as it works by using the index of an element and joining it to other elements
    using a positive or negative index.
    """
    index_of_item = clean_list.index("your chosen item")
    clean_list[:index_of_item] = [' '.join(clean_list[:index_of_item])]  # joins together every element from start to the index of the item

    # to join elements mid-list:
    another_index = clean_list.index("another item")  # date concatenation
    date_start = another_index - 3
    date_end = another_index
    clean_list[date_start:date_end] = [' '.join(clean_list[date_start:date_end])]  # joins the 3 elements before 'another item' index
    return clean_list