Write descriptions of parameters to the documentation file.

    Parameters
    ----------
    sections : list
        Names of parameters sections.
    descriptions : list
        Structured descriptions of parameters.
    params_rst : string
        Path to the file with parameters documentation.

def gen_parameter_description(sections, descriptions, params_rst):
    """Write descriptions of parameters to the documentation file.

    Parameters
    ----------
    sections : list
        Names of parameters sections.
    descriptions : list
        Structured descriptions of parameters.
    params_rst : string
        Path to the file with parameters documentation.
    """
    def parse_check(check, reverse=False):
        """Parse the constraint.

        Parameters
        ----------
        check : string
            String representation of the constraint.
        reverse : bool, optional (default=False)
            Whether to reverse the sign of the constraint.

        Returns
        -------
        pair : tuple
            Parsed constraint in the form of tuple (value, sign).
        """
        try:
            idx = 1
            float(check[idx:])
        except ValueError:
            idx = 2
            float(check[idx:])
        if reverse:
            reversed_sign = {'<': '>', '>': '<', '<=': '>=', '>=': '<='}
            return check[idx:], reversed_sign[check[:idx]]
        else:
            return check[idx:], check[:idx]

    params_to_write = []
    for section_name, section_params in zip(sections, descriptions):
        params_to_write.append('{0}\n{1}'.format(section_name, '-' * len(section_name)))
        for param_desc in section_params:
            name = param_desc['name'][0]
            default_raw = param_desc['default'][0]
            default = default_raw.strip('"') if len(default_raw.strip('"')) > 0 else default_raw
            param_type = param_desc.get('type', param_desc['inner_type'])[0].split(':')[-1].split('<')[-1].strip('>')
            options = param_desc.get('options', [])
            if len(options) > 0:
                options_str = ', options: ``{0}``'.format('``, ``'.join([x.strip() for x in options[0].split(',')]))
            else:
                options_str = ''
            aliases = param_desc.get('alias', [])
            if len(aliases) > 0:
                aliases_str = ', aliases: ``{0}``'.format('``, ``'.join([x.strip() for x in aliases[0].split(',')]))
            else:
                aliases_str = ''
            checks = sorted(param_desc.get('check', []))
            checks_len = len(checks)
            if checks_len > 1:
                number1, sign1 = parse_check(checks[0])
                number2, sign2 = parse_check(checks[1], reverse=True)
                checks_str = ', constraints: ``{0} {1} {2} {3} {4}``'.format(number2, sign2, name, sign1, number1)
            elif checks_len == 1:
                number, sign = parse_check(checks[0])
                checks_str = ', constraints: ``{0} {1} {2}``'.format(name, sign, number)
            else:
                checks_str = ''
            main_desc = '-  ``{0}`` :raw-html:`<a id="{0}" title="Permalink to this parameter" href="#{0}">&#x1F517;&#xFE0E;</a>`, default = ``{1}``, type = {2}{3}{4}{5}'.format(name, default, param_type, options_str, aliases_str, checks_str)
            params_to_write.append(main_desc)
            params_to_write.extend([' ' * 3 * int(desc[0][-1]) + '-  ' + desc[1] for desc in param_desc['desc']])

    with open(params_rst) as original_params_file:
        all_lines = original_params_file.read()
        before, start_sep, _ = all_lines.partition('.. start params list\n\n')
        _, end_sep, after = all_lines.partition('\n\n.. end params list')

    with open(params_rst, "w") as new_params_file:
        new_params_file.write(before)
        new_params_file.write(start_sep)
        new_params_file.write('\n\n'.join(params_to_write))
        new_params_file.write(end_sep)
        new_params_file.write(after)