The function f is given by
$$\mathrm { f } ( x ) = x ^ { \frac { 1 } { 7 } } \left( x ^ { 2 } - x + 1 \right)$$
Find the fraction of the interval $0 < x < 1$ for which $\mathrm { f } ( x )$ is decreasing.
A $\frac { 2 } { 15 }$
B $\frac { 1 } { 5 }$
C $\frac { 1 } { 3 }$
D $\frac { 1 } { 2 }$
E $\frac { 2 } { 3 }$
F $\frac { 4 } { 5 }$
G $\frac { 13 } { 15 }$