human
Complete this python program:
def correlation_matrix(data):
assistant
#Here is the Python code you requested.

    """returns the num_columns x num_columns matrix whose (i, j)th entry
    is the correlation between columns i and j of data
    """
    (_, num_columns) = shape(data)
    def matrix_entry(i, j):
        return correlation(get_column(data, i), get_column(data, j))
    return make_matrix(num_columns, num_columns, matrix_entry)