def get_min(value_type, values):
    assert value_type in ['integer', 'float', 'string', 'timestamp', 'unknown', None]

    known_vals = []
    for val in values:
        if not typer.is_unknown(val):
            try:
                if value_type == 'integer':
                    known_vals.append(int(val))
                elif value_type == 'float':
                    known_vals.append(float(val))
                else:
                    known_vals.append(val)
            except ValueError:
                pass                       # ignore invalid values

    # next return the minimum value
    try:
        return str(min(known_vals))
    except ValueError:
        return None
Returns the minimum value of the input.  Ignores unknown values, if
dataset/ETHPy150Open kenfar/DataGristle/gristle/field_misc.py/get_min