Find the Exact Value of the Expression $\sin ^ { - 1 } \left[ \sin \left( \frac { 6 \pi } { 7 } \right) \right]$

Multiple Choice

Find the exact value of the expression. Do not use a calculator.
- $\sin ^ { - 1 } \left[ \sin \left( \frac { 6 \pi } { 7 } \right) \right]$

A) $\frac { \pi } { 7 }$
B) $\frac { 7 } { 6 \pi }$
C) $\frac { 6 \pi } { 7 }$
D) $\frac { 7 } { \pi }$