import re


def split_str_to_field(input_str):
    """Split the input_str into 2 parts, the field name and field body.

    The split is based on this regex format: :field_name: field_body.
    """

    regex_pattern = "((^:{1}.*:{1})(.*))"
    field_name = None
    field_body = None

    if input_str is None:
        return field_name, field_body

    regex_output = re.match(regex_pattern, input_str)

    if regex_output is None and len(input_str) > 0:
        field_body = input_str.lstrip(' ')

    if regex_output is not None:
        field = regex_output.groups()
        field_name = field[1].strip(':')
        field_body = field[2].strip()

    return field_name, field_body