We should accept any Tables-compatible table as input, instead of only accepting DataFrames

[DilumAluthge]

Tables refers to the Tables.jl package.

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We should accept any Tables-compatible table as input, instead of only accepting DataFrames.

If the input is already a DataFrame, there's nothing extra we need to do. If the input is not a DataFrame, check if it is a Tables-compatible table. If it isn't a Tables-compatible table, throw an error. If it is a Tables-compatible table, convert it to a DataFrame.

Here is some example code.

using DataFrames: DataFrame
import Tables

function my_cool_function(df::DataFrame)
    # do stuff
end

function my_cool_function(input_object)
    assert_is_table(input_object)

    # convert `input_object` to a `DataFrame`
    df = DataFrame(input_object)::DataFrame

    # Assert that `df` is in fact a `DataFrame`
    df::DataFrame

    return my_cool_function(df)
end

function assert_is_table(x)
    if !Tables.istable(x)
        msg = "Input must be a table, but $(typeof(x)) is not a table"
        throw(ArgumentError(msg))
    end
    return nothing
end

[AshlinHarris]

#40