Code note recognizing ColumnDataSource for what it is

I want to change the data source of a simple line plot depending on what the user picks from a dropdown menu.

I have 2 dataframes, the weight and age of myself and my boyfriend.

my_weight = [60,65,70] 
my_age = [21,22,25]

d_weight = [65,70,80] 
d_age = [21,22,25]

me = pd.DataFrame(list(zip(my_weight, my_age)), 
               columns =['weight', 'age'], index=None) 

dillon = pd.DataFrame(list(zip(d_weight, d_age)), 
               columns =['weight', 'height'], index=None)

I turn these two dataframe into ColumnDataSource objects, create my plot and line, add my dropdown and jslink. There is also a demo slider to show how I can change the line_width of my line.

from bokeh.models import ColumnDataSource
from bokeh.core.properties import Any, Bool, ColumnData

pn.extension()

source = ColumnDataSource(me, name="Me")
source2 = ColumnDataSource(dillon, name="Dillon")
# print("Me: ", source.data, "Dillon: ", source2.data)

plot = figure(width=300, height=300)
myline = plot.line(x='weight', y='age', source=source, color="pink")

width_slider = pn.widgets.FloatSlider(name='Line Width', start=0.1, end=10)
width_slider.jslink(myline.glyph, value='line_width')

dropdown2 = pn.widgets.Select(name='Data', options=[source, source2])
dropdown2.jslink(myline, value='data_source')

pn.Column(dropdown2, width_slider, plot)

When I run this code, I get the error

ValueError: expected an instance of type DataSource, got ColumnDataSource(id='5489', ...) of type str

with the error occurring from the dropdown2 section of code.

Whats preventing the code from recognizing source and source2 as ColumnDataSource() objects? What is meant by got ColumnDataSource(id='5489', ...) of type str? How is it a string?