Feat request: join multiple obs_seq instances.

[hkershaw-brown]

Question:

• is it sufficient to join the data frames?
• is a blank obs_seq instance necessary to fill up with obs sequence, or just join existing obs sequence instances?

just dataframes:

class obs_sequence:
    ...
    def join_obs_sequences(self, obs_sequences):
        """Join multiple obs_sequence instances.

        Args:
            obs_sequences (list): List of obs_sequence instances.

        Returns:
            pandas.DataFrame: Joined DataFrame of all obs_sequences.
            
        """
        return pd.concat([obs.df for obs in obs_sequences])

obs_seq1 = obs_sequence('/path/to/obs_seq1.ascii')
obs_seq2 = obs_sequence('/path/to/obs_seq2.ascii')
obs_seq3 = obs_sequence('/path/to/obs_seq3.ascii')

joined_df = obs_seq1.join_obs_sequences([obs_seq2, obs_seq3])