def sum_from(m, n):
    """
    What comes in:  The arguments are two integers m and n, with m <= n.
    What goes out:  Returns the sum of the integers from m to n,
      inclusive.
    Side effects:   None.
    Example:
        sum_from(6, 9) returns 6 + 7 + 8 + 9, that is, 30.
    """
    # -------------------------------------------------------------------------
    # DONE: 3. Implement and test this function.
    #          Tests have been written for you (above).
    #
    # IMPORTANT:  Your solution MUST
    #   use an explicit    for ... in range(...):     statement
    #
    # IMPORTANT: As in previous problems in this session,
    #   you must NOT use the 2 or 3-parameter versions
    #   of the RANGE expression, if you happen to know them.
    # -------------------------------------------------------------------------
    answer_from_my_code = 0
    for k in range(n-m+1):
        if m <= n:
            answer_from_my_code = answer_from_my_code+m+k
    return answer_from_my_code