import math


def myfloor(x, base=10):
    """
    Returns the lower-bound integer of 'x' in base 'base'

    Parameters
    ----------
    x: float
        number to be approximated to closest number of 'base'

    base: float
        base used to calculate the closest 'smallest' number

    Returns
    -------
    n_low: float
        Closest float number to 'x', i.e. lower-bound float.

    Example
    -------
    >>>> myfloor(12, 5)
    >>>> 10
    """
    n_low = float(base*math.floor(float(x)/base))

    return n_low