Adding support to pickup class based css rules.

[vkbsb]

• updated the matplotlib converter to pickup styling based on class as well.
  Current implementation picks up the details based on id. Which is still needed if there is an override but there are scenarios where the class styling has to be picked for table to look good.
  Used the following code to validate that this is working..

import numpy as npy
import pandas as pd
import dataframe_image as dfi

col_headers = {
    "selector": ".col_heading, thead",
    "props": "color: white; background-color: #1d5632; \
            font-size: 11px"
    }
col_data = {
    "selector": ".data",
    "props": "color: black; background-color: #f4f4f4; \
            font-size: 11px"
}

x,y,z = npy.random.random((3,3))
df = pd.DataFrame({
    "x":x[0:],
    "y":y[0:],
    "z":z[0:]
})
styled_df = df.style.set_table_styles([col_headers, col_data])
dfi.export(styled_df, "df_style.png", table_conversion="matplotlib")


output = {
    'Metric': ['P50_FPS', 'Batt_Drop(PM)', 'Temp_Inc(PM)'], 
    'Low': [19.58858, 0.47901234567901235, 0.2906172839506173], 
    'Mid': [29.933165, 0.3128301033724491, 0.22643293121519142], 
    'High': [29.924354, 0.36855614395331243, 0.2592294391008322], 
    'Ultra': [44.800098500000004, 0.3901357466063348, 0.3003981900452488]
    }
df = pd.DataFrame(output)
df = df.apply(lambda x: round(x, 2))
styled_df = df.style.format(precision=2).hide(axis='index')
styled_df.set_caption("Hello World")
styled_df.set_properties(subset=["Low", "High"], **{'font-size': '14pt', 'width':'40px', 'background-color':'lightblue', 'padding':'10px', 'text-align':'center'})
styled_df.set_properties(subset=["Mid", "Ultra"], **{'color': 'red', 'width':'40px', 'background-color':'lightyellow', 'padding':'10px', 'text-align':'center'})
dfi.export(styled_df, "df_style_1.png", table_conversion="matplotlib")