Fixes # .

Summary/Motivation:

This relaxes the requirements in the DataFrameInitializer to accept multi-column DataFrame objects. This allows DataFrames to be used directly to initialize 2-dimensional objects where the second dimension are the column labels.

For example, the following will work:

from pyomo.environ import *
import pandas as pd

df = pd.read_csv('data.csv')

m = ConcreteModel()
m.R = Set(initialize=df.index)
m.C = Set(initialize=list(df))
m.data = Param(m.R, m.C, initialize=df)

Changes proposed in this PR:

• Relax restriction on multi-column DataFrames (and add tests)

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