Revert due to performance "ENH: TCPrinter: Use sympy as_set() instead of custom function"
Revert due to performance "ENH: TCPrinter: Use sympy as_set() instead of custom function"

This reverts commit e23f6fd4c2aa13a3cc6154dbb3bc4ced96eb4996.

tkphd/pycalphad,tkphd/pycalphad,tkphd/pycalphad