Write the given sequence to the given path, using the file format implied 
    by the path's file extension.

    Arguments
    =========
    path: str or pathlib.Path
        The name of the file to create.  Allowed extensions are:
        
        - *.fa, *.fas, *.fasta
        - *.tsv, *.csv
        - *.xlsx

    seqs: dict
        A mapping of names to sequences, which can be either protein or DNA.

def write_sequences(path, seqs):
    """
    Write the given sequence to the given path, using the file format implied 
    by the path's file extension.

    Arguments
    =========
    path: str or pathlib.Path
        The name of the file to create.  Allowed extensions are:
        
        - *.fa, *.fas, *.fasta
        - *.tsv, *.csv
        - *.xlsx

    seqs: dict
        A mapping of names to sequences, which can be either protein or DNA.
    """
    path = Path(path)

    if path.suffix in ('.fa', '.fas', '.fasta'):
        write_sequences_to_fasta(path, seqs)

    elif path.suffix in ('.tsv', '.csv'):
        write_sequences_to_tsv(path, seqs)

    elif path.suffix in ('.xlsx',):
        write_sequences_to_xlsx(path, seqs)

    else:
        raise scripting.UserError("""\
'{}' has unknown output filetype '{}'.  Please provide a path with one of the 
following extensions:

- *.fa, *.fas, *.fasta
- *.tsv, *.csv
- *.xlsx
""".format(path, path.suffix))