Can not create constraints when a coordinate is named "sign"

[tom-welfonder]

When I name a coordinate "sign", an error is raised when I try to create an constraint.

Here a short example to reproduce the issue:

import pandas as pd
import linopy

coords = [pd.Index(range(10), name="sign")]

m = linopy.Model()
x = m.add_variables(lower=0, coords=coords, name="x")
x>=0

Error message:

File ~/.env/lib/python3.10/site-packages/linopy/constraints.py:295, in __repr__(self)
    293         else:
    294             line = f"{print_coord(coord)}: None"
--> 295         lines.append(line)
    296 lines = align_lines_by_delimiter(lines, list(SIGNS_pretty.values()))
    298 shape_str = ", ".join(f"{d}: {s}" for d, s in zip(dims, dim_sizes))

KeyError: 0

When I add at least one additional coordinate to coords, a different error is raised:

File ~/.env/lib/python3.10/site-packages/linopy/constraints.py:295, in __repr__(self)
    293         else:
    294             line = f"{print_coord(coord)}: None"
--> 295         lines.append(line)
    296 lines = align_lines_by_delimiter(lines, list(SIGNS_pretty.values()))
    298 shape_str = ", ".join(f"{d}: {s}" for d, s in zip(dims, dim_sizes))

IndexError: too many indices for array: array is 1-dimensional, but 2 were indexed

I was able to reproduce some (different) errors for the names: "labels", "coeffs", "vars", "rhs". I found these in constraint.py in line 671:

dataset_attrs = ["labels", "coeffs", "vars", "sign", "rhs"]