Get a number (as a number or string), and return it as a string,
using formats defined as arguments:
- decimal_sep: Decimal separator symbol (for example ".")
- decimal_pos: Number of decimal positions
- grouping: Number of digits in every group limited by thousand separator.
- For non-uniform digit grouping, it can be a sequence with the number
of digit group sizes following the format used by the Python locale
module in locale.localeconv() LC_NUMERIC grouping (e.g. (3, 2, 0)).
- thousand_sep: Thousand separator symbol (for example ",")