Add table() method for formatted HTML table visualization

[nitininhouse]

Description

Added table() method to Visdom for displaying formatted HTML tables. Renders structured data with styled headers, alternating row colors, hover effects, and monospace font for clean presentation.

Motivation and Context

Tables are essential for displaying structured training metrics, results summaries, and comparison data. This feature eliminates manual HTML formatting and provides a consistent, visually appealing way to visualize tabular data within Visdom.

closes #1081

How Has This Been Tested?

Tested with sample training data:

viz.table(
    headers=['Epoch', 'Loss', 'Accuracy'],
    data=[[1, 0.45, 0.92], [2, 0.32, 0.94], [3, 0.21, 0.96]],
    opts={'title': 'Training Results'}
)

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[Copilot]

Pull request overview

Adds a new table() helper to the Visdom Python client to render structured data as a styled HTML table via the existing text() endpoint.

Changes:

• Introduces Visdom.table(headers, data, ...) to generate HTML <table> markup from headers + rows
• Adds basic table styling (header background, alternating row colors, monospace font)
• Performs basic input validation and sets a default window title

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[Copilot]

Header and cell values are interpolated into HTML without escaping. If any values contain HTML (e.g., <script>), this will be rendered/executed in the Visdom UI (XSS risk). Escape h and cell with html.escape(str(...), quote=True) (or an equivalent escaping utility already used in the project) before inserting into the <th>/<td> markup.

[Copilot]

Header and cell values are interpolated into HTML without escaping. If any values contain HTML (e.g., <script>), this will be rendered/executed in the Visdom UI (XSS risk). Escape h and cell with html.escape(str(...), quote=True) (or an equivalent escaping utility already used in the project) before inserting into the <th>/<td> markup.

[Copilot]

Using assert for runtime input validation is brittle because asserts can be disabled with Python optimizations (-O), which would remove these checks in production. Prefer raising TypeError/ValueError with the same messages (or more specific ones) so validation is enforced consistently.

Suggested change

	assert isinstance(headers, list), "headers should be a list"
	assert isinstance(data, list), "data should be a list of lists"
	for row in data:
	assert isinstance(row, list), "each row in data should be a list"
	assert len(row) == len(headers), \
	"each row length must match number of headers"
	if not isinstance(headers, list):
	raise TypeError("headers should be a list")
	if not isinstance(data, list):
	raise TypeError("data should be a list of lists")
	for row in data:
	if not isinstance(row, list):
	raise TypeError("each row in data should be a list")
	if len(row) != len(headers):
	raise ValueError("each row length must match number of headers")

[Copilot]

Building rows_html via repeated string concatenation in a loop is O(n²) in total copied characters for large tables. Use a list accumulator (append each <tr>...</tr>) and ''.join(rows) at the end to keep it O(n) and reduce allocations.

[Copilot]

The PR description mentions 'hover effects', but the generated markup only sets static inline styles (no :hover styling and no JS). Either update the description to match the current implementation or add a hover style (e.g., via embedded <style> and a class-based selector) so the feature matches the stated behavior.

[Copilot]

There appears to be an extra blank line/trailing whitespace introduced around the end of the preceding call. Please remove trailing whitespace and keep formatting consistent to avoid lint/format churn in future diffs.

Suggested change

	)
	)

[nitininhouse]

Hello @mariobehling @marcoag @norbusan
Could you please review it