Convert Python dictionary to string, which is passed to C API.

def param_dict_to_str(data):
    """Convert Python dictionary to string, which is passed to C API."""
    if data is None or not data:
        return ""
    pairs = []
    for key, val in data.items():
        if isinstance(val, (list, tuple, set)) or is_numpy_1d_array(val):
            pairs.append(str(key) + '=' + ','.join(map(str, val)))
        elif isinstance(val, string_type) or isinstance(val, numeric_types) or is_numeric(val):
            pairs.append(str(key) + '=' + str(val))
        elif val is not None:
            raise TypeError('Unknown type of parameter:%s, got:%s'
                            % (key, type(val).__name__))
    return ' '.join(pairs)