I'm using python-docx to create a document with a table I want to populate from textual data. My text looks like this:

01:02:10.3 
a: Lorem ipsum dolor sit amet,  
b: consectetur adipiscing elit.
a: Mauris a turpis erat. 
01:02:20.4 
a: Vivamus dignissim aliquam
b: Nam ultricies
(etc.)

I need to organize it in a table like this (using ASCII for visualization):

+---+--------------------+---------------------------------+
|   |         A          |                B                |
+---+--------------------+---------------------------------+
| 1 | 01:02:10.3         | a: Lorem ipsum dolor sit amet,  |
| 2 |                    | b: consectetur adipiscing elit. |
| 3 |                    | a: Mauris a turpis erat.        |
| 4 | ------------------ | ------------------------------- |
| 5 | 01:02:20.4         | a: Vivamus dignissim aliqua     |
| 6 |                    | b: Nam ultricies                |
+---+--------------------+---------------------------------+

however, I need to make it so everything after "a: " is bold, and everything after "b: " isn't, while they both occupy the same cell. It's pretty easy to iterate and organize this the way I want, but I'm really unsure about how to make only some of the lines bold:

IS_BOLD = { 
    'a': True
    'b': False
}

row_cells = table.add_row().cells

for line in lines: 
    if is_timestamp(line): # function that uses regex to discern between columns
        if row_cells[1]:
            row_cells = table.add_row().cells

        row_cells[0].text = line

    else 
        row_cells[1].text += line

        if IS_BOLD[ line.split(":")[0] ]:
            # make only this line within the cell bold, somehow.

(this is sort of pseudo-code, I'm doing some more textual processing but that's kinda irrelevant here). I found one probably relevant question where someone uses something called run but I'm finding it hard to understand how to apply it to my case.

Any help? Thanks.