def str_fabs(number_str):
    """Remove the leading minus sign (if any) from a string representing a
    number. It behaves in a very similar way to `str(fabs(float(number_str)))`,
    except that it preserves the representation of `number_str` (precision,
    scientific notation, etc.). The input parameter must represent a valid
    float.

    :param str number_str: a number, as a string
    :returns: the absolute value of the number represented by `number_str`

    Examples:

    >>> str_fabs('-1.5')
    '1.5'
    >>> str_fabs('-1e-30')
    '1e-30'
    >>> str_fabs('-1.0e24')
    '1.0e24'
    >>> str_fabs('56.5')
    '56.5'
    >>> str_fabs('   -44  ')  # spaces are tolerated
    '44'
    """
    number_str = number_str.strip()
    if number_str[0] == '-':
        return number_str[1:]
    return number_str
