def join_sentences_by_label(grouped_sentences_df, label_col="topic_name", sentence_col="sentence"):
    """
    Function used to join sentences into texts. Sentences are grouped by topics

    ---

    **Arguments**\n
    `grouped_sentences_df` (DataFrame): DataFrame with sentences groped by topics and which contains
    *label_col*, *sentence_col* columns. \n
    `label_col` (String): Name of the label column in data frame. Default value = "topic_name".\n
    `sentence_col` (String): Name of the sentence column in data frame. Default value = "sentence".\n

    ---

    **Returns**\n
    `joined_df` (DataFrame): DataFrame with columns *label_column_name*, *joined_sentences*.
    """

    return grouped_sentences_df.groupby([label_col])[sentence_col].apply(' '.join).reset_index()