
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given that \( F_1 \) and \( F_2 \) are the left and right foci of the ellipse \( C: \frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1 \) where \( a > b > 0 \), and \( P \) is a point on the ellipse \( C \). The incenter of triangle \( \triangle F_{1}PF_{2} \) is \( I \). If there exists a real number \( \lambda \) such that:
$$
(1+\lambda) \overrightarrow{PF_{1}} + (1-\lambda) \overrightarrow{PF_{2}} = 3 \overrightarrow{PI},
$$
then the eccentricity of the ellipse \( C \) is $\qquad$ .

Present the answer in LaTex format: \boxed{Your answer}
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