def _unit_change(value_to_be_changed, unit):
    """
    Changes value based on given unit
    Parameters
    ----------
    value_to_be_changed : float
        value that is returned once it is changed
    unit : string
        unit the value should be converted to
    """
    if unit is 'micro':
        return value_to_be_changed * 1e6
    elif unit is 'nano':
        return value_to_be_changed * 1e9