chi_angles_mask

If there is a mask of corresponding torsion angle in the amino acid. A two-dimensional array, the length of first dimension is 20, representing 20 different amino acids, consistent with the order of 'restype_order'. The second dimension has a length of 4, and each amino acid has a maximum of four side chain torsion angles, with a value of 1.0 indicating the existence of the torsion angle and 0.0 indicating the absence of the torsion angle.

value				amino acid
0.0	0.0	0.0	0.0	#ALA
1.0	1.0	1.0	1.0	#ARG
1.0	1.0	0.0	0.0	#ASN
1.0	1.0	0.0	0.0	#ASP
1.0	0.0	0.0	0.0	#CYS
1.0	1.0	1.0	0.0	#GLN
1.0	1.0	1.0	0.0	#GLU
0.0	0.0	0.0	0.0	#GLY
1.0	1.0	0.0	0.0	#HIS
1.0	1.0	0.0	0.0	#ILE
1.0	1.0	0.0	0.0	#LEU
1.0	1.0	1.0	1.0	#LYS
1.0	1.0	1.0	0.0	#MET
1.0	1.0	0.0	0.0	#PHE
1.0	1.0	0.0	0.0	#PRO
1.0	0.0	0.0	0.0	#SER
1.0	0.0	0.0	0.0	#THR
1.0	1.0	0.0	0.0	#TRP
1.0	1.0	0.0	0.0	#TYR
1.0	0.0	0.0	0.0	#VAL